Suey Vanbaarle Bio Notes
From KstructIB
Topic 1 and 7: Cells
1.1 cell theory ----------
Robert Hooke (1665)- Cells were first described by the English scientist Robert Hooke, who in 1665 published a book about his findings. Hooke had sliced off thin sections of cork. With a microscope of his own design he was able to see the minute, boxlike units of which the cork was made up. Hooke called these structures because he thought the Boxes looked like monastery cells.
Anton van Leeuwenhoek (1650-1700)- first observed the protists. Using a simple lens (x200) observes unicellular organisms and nuclei. Describes bacteria as "animalcules". By means of his extraordinary ability to grind lenses, Anthony van Leeuwenhoek greatly improved the microscope as a scientific tool. This led to his doing a vast amount of innovative research on bacteria, protozoa, and other small life-forms that he called (tiny animals).
Matthias Schleiden (1838)- deduced his theory "phytogenesis"- that all living things are made up of cells or their derivatives.
Theodore Schwann (1839)- together with Schleiden deduced the cell theory- that all animals and plants were made of cells, and that within an organism these cells are identical.
Rudolph Virchow (1855)- all cells arise from pre-existing cells.
Light microscopes- three advantages: 1) we can distinguish the larger structures within eukaryotic cells and cal also distinguish individual prokaryotic cells. 2) user-friendly: small, portable, slides are easy to prepare, are relatively cheap to purchase and to operate. 3) living as well as dead material may be viewed and material is rarely distorted by preparation.
Electron microscopes-two advantages: 1) magnifies objects over 500,000x 2) has a resolving power for biological specimens of around 1 nanometer. Thus, it is possible to investigate a greather depth of field.
'Resolution'- ability to perceive fine detail and is expressed as the minimum distance between two points that can be distinguished as separate, distinct points rather than viewed as one blurred single points. Depends on the quality of the lenses and upon the wavelength used.
'Magnification'- the ratio of the size of the image viewed under the microscope to the actual size of the object.
Organelle- An internal cell structure that performs a specific function.
Relative sizes of small stuff- molecules-1 nanometer ~ thickness of membranes-10 nanometers ~ viruses- 100 nanometer ~ bacteria-1micrometer ~ organelles-up to 10 micrometers ~ cells-up to 100 micrometers
Surface area to volume ratio- as volume decreases, the ratio of surface area to volume increases rapidly. The more active a cell's metabolism, the more materials must be exchanged with the environment, if the cell is to continue to function. Thus, the smaller a cell is, the faster materials can be moved into and out of the cell. Larger cells require larger quantities of materials moved into the cell to meet the larger volume of living matter, but it has a smaller surface-to-volume ratio.
1.2: Prokaryotic cell structure ----------
Ribosomes- small cytoplasmic granules found in all cells. They are smaller than eukaryotic ones. They occur either singly or in groups called polysomes. They are made up of RNA and protein and are important in protein synthesis.
Mesosome- these resemble the mitochondria in eukaryotic cells. They are infoldings of the cell membrane that are important in respiration.
Slime capsule- surrounds the cell wall of the bacteria
Cell wall- gives structure to the bacteria cell
Flagellum- movement
Cell surface membrane- controls the movement of things in and out of the cell, also protects the organelles inside the cell from the outside environment
Plasmid- an extrachromosomal, independentrly replicating, small, circular DNA molecule.
Naked nucleic acid- Contains the hereditary information of the cell. Important because it regules protein production.
1.3 Eukaryotic cell structure ----------
Endosymbiosis- The theory that mitochondria and chloroplasts are descended from specialized bacteria. This is because these organelles both contain their own DNA and this DNA is present in a single, continuous molecule, like the DNA of bacteria. Many of the enzymes contained in the cell membranes of bacteria are found in the mitochondrial membranes. Also, they both have their own ribosomes that resemble those of bacteria. Mitochondria can only be produced by mitochondria, like cells from cells. Probably these organelles used to be simple bacteria and were swallowed up by bigger bacteria who could not digest them. In turn these organelles provided the cell with energy in return for protection etc. and turned into an organelle.
Ribosome- nonmembranous granules composed of RNA and protein- some are attached to ER. Manufacture proteins.
Rough endoplasmic reticulum- network of internal membranes extending through cytoplasm; forms system of tubes and vesicles. Rough sort contains ribosomes which stud the outer surfaces. Manufactures and transports proteins.
lysosome- membranous sacs containing hyrolytic enzymes. Hyrolyze proteins and other matierals, including ingested bacteria, and also play a role in cell death by 'digesting' the whole cell.
Golgi Apparatus- stacks of flattened membranous sacs. Packages secretions and manufactures lysosomes.
Mitochondrion- site of the most of the reactions of cellular respiration; power plants of the cell.
Nucleus- large spherical structure surrounded by a double nuclear membrane; contains nucleolus and chromosomes. Control center of the cell; contains genetic material.
Chloroplast- contains chlorophyll and is present only in plant cells. Is involved in photosynthesis. Differences between allllllll kinds of different cells
Two similarities between prokaryotic and eukaryotic- 1) both contain a cell membrane, two phospholipid sheets. 2) both contain the genetic information- that directs a cell's activities and enables it to reproduce.
Two differences between the eukaryotic nucleus and prokaryotic nuclear material- in a prokaryotic cell, the genetic material is in the form of a large, circular molecule of DNA, with wihich a vaiety of proteins are loosely associated. This molecule is known as the chromosome. In eukaryotic cells, the DNA is linear, forming a number of distinct chromosomes; morover, it is tightly bound to special proteins known as histones, which are an integral part of the chromosome structure. Within the eukaryotic cell, the chromosomes are surrounded by a double membrane, the nuclear envelope, but in eukaryotic cells the genetic information is contained within a region called the nucleoid.
Three differences between plant and animal cells- Plant cells contain a tough, slightly elastic cellulose cell wall in addition to the cell membrane, but this cell wall is a non-living part of the cell. Also, plant cells contain chloroplasts for photosynthesis, animal cells do not. Animal cells contain centrioles which are involved in cell reproduction, plant cells do not. Also, pits and plasmodesmata are found in the cell wall of plant cells, and plant cells also contain a much larger, centralized vacuole.
Plant cell wall- contains cellulose which is strong tough material. This is important because cells of plants need more structure so that it doesn't move- the cell wall provides this. It also contains pits and plasmodesmata in the cell wall so that the plant cell can 'communicate' with other plant cells.
1.4 and 7.1 Membranes ----------
Hydrophobic and hydrophillic- Membranes are made up of a lipid bilayer that includes two sheets of phospholipid molecules. A phospholipid molecule is made up of two hydrophobic fatty acid tails and a phosphate head, which is hydorphillic. The tails are faced inwards, to each other because they are hydrophobic, while the heads face outwards, since they are water-loving.
Biomembranes- this refers to the lipid bilayer mentioned above. This type of membrane is found on all membranous structures- the nucleus, rough endoplasmic retuculum, golgi apparatus, and cell surface membrane.
Vesicles- vesicles are involved in cell-mediated transport (see endocytosis and exocytosis). Vesicles move from the golgi complexes to the surfaces of the cell. When a vesicle reaches the cell surface, its membrane fuses with the membrane of the cell, thus expelling its contents to the outside. This is exocytosis. In endocytosis. material to be taken into the cell induces the membrane to bulge inward, producing a vesicel enclosing the substance.
Diffusion- The net movement of suspended or dissolved particles down a concentratin gradient as a result of the random spntaneous movements of individual particles; the process tends to distribute the particles uniformly throughout a medium.
Osmosis- the diffusion of water across a selectively permeable membrane. In the absence of other factors that affect the water potential, the net movement of water is from the side containing a lower concentration of solute to the side containing a higher concentration.
Passive transport- any transport that goes with a concentration gradient, ie, from a high concentration to a low concentration. Diffusion and osmosis are both examples of passive transport. Passive transport does not require any energy to carry out.
Active transport- This type of transport goes against the concentration gradient and thus requires energy to carry out. It is usually carried out by specific proteins embedded in the cell membrane, called transport proteins. Without active transport glucose could not be transported.
Membrane proteins- two basic types: an alpha helix, and a globular tertiary structure. allow different types of molecules to enter and leave the cell. Membrane proteisn also act as antibody recogniztin sites, hormone binding sites, catalysts for biochemical reactions and sites of electron carriers.
Endocytosis and exocytosis- Endocytosis is a cellular process in which the material to be taken into the cell induces the membrane to form a vacuole enclosing the material; the vacuole is released into the cytoplasm. Includes phagocytosis, which is the enocytosis of solid particles, pinocytosis, which is the endo. of liquids. Exocytosis is a cellular process in which partiulate matter or dissolved substances are enclosed in a vacuole and transported to the cell surface; there, the membrane of the vacuole fuses with the cell membrane, expelling the vacuole's contents to the outside.
1.5 and 7.2 Cell Division- mitosis ----------
Mitosis- Nuclear devision chaaracterized by chromosome replication and formation of two identical daughter nuclei-this is the process that creates new cells- all cells can only come from old cells.
Cell cycle- The cell cycle consists of five major phases: G1, S, G2, mitosis, and cytokinesis. G1, S and G2 are known as interphase.
Interphase- Before a cell can begin mitosis and actually dicide, it must replicate its DNA, synthesize more of the histones and other proteins associated wwith the DNA in the chromosomes, pdoduce a supply of organelles adequate for two daughter cells, and assemble the structures needed to carry out mitosis and cytokinesis. This all happens in interphase.
S (synthesis)- during this phase the DNA is replicated, and also many of the histones and other DNA-associated proteins are synthesized.
G1 phase- a period of intense biochemical activity. The cell increaes in seize, and its enzymes, ribosomes, mitochondria, and other cytoplasmic molecules and structures also increase in number. Some of the cellular structures can be syntesized enteriely from scratch by the cell, such as microfilaments, mircrotubules, etc. Membranous structures are all derived from the endoplasmic reticulum.
G2 phase- The final preparations for cell dicision occur. The newly replicated chromosomes, which are dispersed in the nucleus in the form of threadlike strands of chromatin, slowly begin to coil and condense into a compact form; this condensation appears to be necessary for the complex movements and separation of the chromosomes that will occur in mitosis. Replication of the centriole pair is completed, with the two mature entriole pairs lying just outside the nuclear envelope. The cell begins to assemble the special strcutures required for the allocation of a complete set of chromosomes to each daughter cell during mirosis and for the separation of the two daughter cells during cytokinesis.
Spindle- a three-dimensional football shaped structure, consisting of two groups of microtubules. 1. polar fibres- reach from each end of the pole 2. kinetochore fibers, which are attached to the kinetochores of the replicated chromosomes. Each pole is marked by a different pair of centrioles. Additional fibres which go past the poles are known as the aster. They may brace the poles of the spindles against the cell membranes. Most of the tubulin appears to be borrowed from the cytoskeleton.
Mitosis- consists of the following stages:
Prophase -chromosome condenses -nucleolus fades -nuclear membrane breaks -spindle forms -centrioles move to poles -chromosomes move to equator (center of cell)
Metaphase -chromosomes at equator
Anaphase -chromosomes separate -chromosomes move to poles
Telophase -chromosomes at poles -spindle fades -nuclear membrane reforms -chromosomes unwind -nucleoli appear Tumors- the result of uncontrolled cell division and that these can occur in any organ.
Mitosis and cytokinesis in animal and plant cells- mitosis can only occur in eukaryotic cells. Also, in animal cells, there are centrioles but not in the plant cell. Basal bodies appear to be used in plants. Basal bodies also play a role in organizing the microtubules of the spindle fibers, spinning them like spiders spin webs. Cells that do not have basal bodies or centrioles also form spindles with microtubules.
Cytokinesis- animal cell- the cell membrane begins to constict along the circumference of the cell in the plane of the equator of the spindle. At first a furrow appears on the surface, this gradually deepens into a groove. Eventually the connection between the daughter cell sdwindles to a slender thread, which soon parts. Plant cells- the cytoplasm is divided at the midline by a series of polysaccharide-containing vesicles produced from the golgi complexes. The vesicles eventually fuse to form a flat, membrane-bound space, the cell plate. As more vesicles fuse, the edges of the growing plate fuse with the membrane of this cell. A layer of polysaccharides is formed between the two daughter cells completing their separation. This layer gets impregnated with pectins and eventually forms the middle lamella. each new cell then creates its own cell wall.
7.3 Differentiation and functional specialisation ----------
Unicellular organisms-carry out all functions of life. Cells in multicellular organisms differentiate to carry out specialized funtions.
Tissue- a group of similar cells organized into a structural and functional unit.
Organ- a body part composed of several tissues grouped together in a structural and functional unit.
Organ system- a group of organs that work together to carry out similar functions. These contain many different organs, which in turn contain many different tissues, which contain many different cells.
Differentiation- cells in multicellular organisms do not all carry out the same task- they are specialized and do only one or some specific tasks. All cells in a multicellular organism have the same genes, so they differentiate by expression of some of their genes and not others. The pathway of differentiation is determined by the cells position relative to others and by chemical gradients.
Topic 2: The chemistry of life Topic 8: DNA and Protein
2.1. Elements of Life ----------
Elements- The three most commonest elements of life are carbon, hydrogen and oxygen. A variety of other elements are needed by living organisms including nitrogen, sulfur, phosphorus, iron and potassium. CHNOPS- carbon hydrogen nitrogen oxygen phosphorus and sulfur. Why important? they form covalent bonds and they can all form bonds with two or more atoms, making possible the formation of the large and complex molecules essential for the structures and functions of living systems.
Nitrogen- This is an important element of amino acids, which are needed for proteins, which are necessary for life in any organism. Nitrogen is also needed in DNA, in the nitrogenous bases.
Sulfur- important component of proteins.
Phosphorus- important component of DNA
Iron- needed for hemoglobin to carry oxygen- which in turn is needed for respiration
Potassium- involved in propagating nerve impulses
Atom- the smallest particle into which a chemical element can be divided and still retain the properties characteristic of the element, consists of a central core, the nucleus, containing protons and neutrons, and electrons that move around the nucleus.
Ions- any atom or small molecule containing an unequal number of electrons and protons and therefore carrying a net positive or net negative charge.
Organic- 1) organisms or living things generally 2) compounds formed by living organisms 3) the chemistry of compounds containing carbon
Structure- made up of two atoms of hydrogen and one atom of oxygen. Each of the hydrogen atoms is linked to the oxygen atom by a covalent bond; that is, the single electron of each hydrogen atom is shared with the oxygen atom, which also contributes an electron to each bond.
Charge- The water molecule as a whole is neutral in charge, having an equal number of electrons and protons. However, the molecule is polar. Because of the very strong attraction of the oxygen nucleus for electrons, the shared electrons of the covalent bonds spend more time around the oxygen nucleus than they do around the hydrogen nuclei. 4 ended- 2 ends are negatively charged and 2 ends are positively charged. Hydrogen bonds- negative end strongly attracted to positive end and other way around.
Properties of Water
High surface tension- a result of the cohesion or clinging together of water molecules. Only mercury has higher surface tension than water!! so its pretty cool. Water adheres strongly to any other charged molecules and to charged surfaces.
Capillary action- When water rises between two close objects ie. two glass slides held together with water in between- the water will rise. Imhibition is the capillary movement of water molecules into substances such as wood or gelatin, and can cause it to swell.
Resistance to Temperature Change- a big input of energy is needed to raise the temperature of water. Thus, it has a high specific heat- the amount of heat required to raise a specific amount of a substance. For water, one calorie is the amount of energy to raise 1 gram of water 1 degree. This is a consequence of the hydrogen bonding. It restricts the movement of the molecule. Why good? Large water bodies will remain stable- so fishes don't turn into ice cubes. Also, cause we have a lot of water inside, it is hard for the sun to raise our temperatures.
Vaporization- change from a liquid to a gas. Water has a high heat of vaporization. This is also because of hydrogen bonds- see resistance to temperature change. The hydrogen bonds have to be broken. This requires a great deal of energy. So how is this property biologically used? Sweating. Vaporization of water carries a great deal of energy away with it.
Freezing- When water turns to ice its density increases. When molecules move around less the spaces between them decrease. But at 4 degrees, the hydrogen molecules come really close together so density actually decreases. This creates an open latticework- the most stable structure for an ice crystal. water as a solid takes up more volume than as a liquid. Good for ponds and lakes- ice floats up to the top, and insulates the water so fishies and amoebas don't die. Good eh?
Good as a solvent- because of polarity of molecule. Tend to separate ionic substances. So they cluster around and segregate the charged ions.
How is it used- As a solvent, for sweating, and also for the transpiration of trees- explanation needed? very thin column of water in the tree- this is how the top of the tree actually gets water. it remains unbroken due to the cohesion of water. and carries minerals etc. up because it is a solvent. At the top of the column water gets evaporated but because of cohesiveness the water gets pulled up the column.
2.2 Carbohydrates, lipids and Proteins ----------
Condensation- a type of chemical reaction in which two molecules join to form one larger molecule, simultaneously splitting out a molecule of water. The biosynthetic reactions in which monomers (eg monosaccharides, amino acids) are joined to form polymers (eg polysaccharides, polypeptides) are condensation reactions.
Thus, monosaccharides- polysaccharides +H2O amino acids-dipeptides +H2O-polypeptides +H2O fatty acids-glycerol+H2O-triglycerides +H2O
Hydrolysis- splitting of one molecule into two by addition of H+ and OH- ions from water.
Solubility- carbohydrates and proteins are soluble because they are hydrophillic. Water molecules are attracted to molecules that have regions of partial positive and negative charge because of covalent bonds. These molecules attract water molecules and thus dissolve in water. They attract water molecules more than they attract each other. Lipids are insoluble because they are hydrophobic; they lack polar regions. The hydrogen bonding of H2O works to exclude those molecules who are nonpolar, such as fats. Thus, nonpolar molecules tend to cluster together in water.
Energy of molecules- lipids contain about twice as much energy as proteins and carbohydrates, by mass.
Monosaccharides- glucose and fructose- are burned or oxidized to yield carbon dioxide and water, which releases energy .
Disaccharides- sucrose, lactose- transport sugars. Sucrose is the form in which sugar is transported in plants from the photosynthetic cells, where it is produced, to other cells of the plant body.
Polysaccharides- cellulose and starch- storage of sugars.
Lipids- 1)storage of energy 2) structural 3) sex hormones
2.3 and 8.6 Enzymes ----------
Enzymes- a globular protein molecule that accelerates a specific chemical reaction.
Active site- the region of an enzyme surface that binds the substrate during the reaction catalyzed by the enzyme.
Metabolic pathways- consist of chains and cycles of enzyme catalysed reactions.
"Lock and key"- only one type of substrate fits into the active site; if a substrate does not fit into the active site then there is no reaction.
"Induced fit" model- The active site is much more flexible than a keyhole. The binding between enzyme and substrate appears to alter the conformation of the enzyme, thus inducing a close fit between the active site and the substrate. It is believed that this induced fit may put some strain on the reacting molecules and so further facilitate the reaction.
How they work- enzymes lower the activation energy of the chemical reactions that they catalyze.
Temperature- the rate of most enzymatic reactions approximately doubles for each 10 degrees rise in temperature and then drops off very quickly above 40 degrees. At higher temperatures, more of the substrate molecules possess sufficient energy to react; the decrease in the reaction rate occurs as the movement and vibration of the enzyme molecule itself increases, disrupting the hydrogen bonds and other relatively fragile forces that maintain its tertiary structure. The enzyme is then said to be denatured. It has lost its three-dimensional structure and cannot function.
Substrate concentration- if the concentration of an enzyme remains constant as the substrate concentration increases, the rate of reaction increases until it approaches a maximum. The maximum rate is attained when all of the enzyme molecules are occupied by substrate molecules.
pH- The conformation of an enzyme depends, among other factors, on attractions and repulsions between negatively charged acidic and positively charged basic amino acids, As the pH changes, these charges change, and so the shape of the enzyme changes until it is so drastically altered that it is no longer functional. More important, probably, the charges of the active site and the substrate are changed so that the binding capacity is affected. The optimum pH for each enzyme differs.
Competitive inhibition- when a molecule is so similar to the substrate molecule that it binds to the active site and prevents the actual substrate from binding with the enzyme. examples- inhibition of butanedioic acid (succinate) dehydrogenase by propanedioic acid (malonate) in the Kreb's cycle.
Non-competitive- when a molecule, an inhibitor molecule, binds to an enzyme, NOT its active site, and changes the conformation of the active site resulting in a change in activity. example- CN- ion inhibition of many enzymes by binding to -SH groups, thereby breaking -S-S- linkages.
Allostery- allosteric interactions are mechanisms by which an enzyme may be temporarily activated or inactivated. It is a form of non-competitive inhibition. An allosteric interaction occur among enzymes that have at least two binding sites, one the active site and another into which a second molecule, known as the allosteric effector, fits. The binding of the effector changes the shape of the enzyme molecule and either activates or inactivates it. Allosteric interactions are frequently involved in feedback inhibition, which is a common means of biological control. In feedback inhibition, one of the products, often last in the series, acts as an allosteric effector, inhibiting the function of one of the enzymes, often the first in the series. Or, in a reaction that may take one of two directions, the effector may act to shunt the reactions along another pathway.
Denaturation- when an enzyme molecule has lost its characteristic 3-d structure.
Applications- Oil digesting bacteria, bacterial extraction of metals from ores, yoghurt, cheese, biological washing powder and tenderizing meat.
2.4 and 8.1 DNA structure ----------
Structure- DNA consists of units called nucleotides. There are four different nucleotides. Each one consists of a deoxyribose 5-carbon sugar, a phosphate group, and a nitrogenous base- adenine, guanine, cytosine, or thymine. The DNA molecule consists of 2 strands twisted together into a double helix, much like a twisted ladder. The phosphate and the sugar molecules make up the sides of the ladder. The phosphate group is joined to the deoxyribose sugar in the nucleotide on the 5' end carbon and to the 3' end carbon of the deoxyribose of the other sugar. The nitrogenous bases make up the steps of the ladder.
The bases of one chain are attracted to the bases of the other chain by means of hydrogen bonds. Adenine and guanine are purines, which are double-ringed, and cytosine and thymine are pyrimidines, which are single-ringed. Adenine can only pair with thymine and cytosine only with guanine. This is known as the base-pair rule. A and T form a soluble hydrogen bond, C and G a triple one. A and T are complementary; G and C also. This is known as the base-pair rule.
Nucleosome- composed of a core of two molecules each of histones H2A, H2B, H3, H4; eight molecules in all- around which the DNA filament is wrapped twice, like thread around a spool. Each nucleosome contains, in addition to the eight histone molecules, about 140 pairs of nucleotides, and the strand of DNA between the nucleosomes contains another 30 to 60 nucleotides.
Genes- only a small percentage of the DNA in the nucleus are actual genes- the majority are just repetition sequences which are protection for viruses.
2.5 and 8.2 DNA replication ----------
replication- semi conservative. Half of the new strand consists of the old strand, the other half is brand new.
Mechanics of replication -Initiation of replication is always at a specific nucleotide sequence. -Special initiator proteins: enzymes called helicases- they break the hydrogen bonds linking the complementary bases at the replication origin, opening up the helix so replication can occur. -topoisomers- break and reconnect one or both strands of the helix, allowing swiveling to occur and thus relieving strain on adjacent portions of the molecule. -Strand-binding proteins attach to the individual strands, holding them apart and preventing kinking. -Replication is always bidirectional, with two replication forks moving in opposite directions away from the origin (replication fork) -primer- beginning of new strand. Formed of nucleotides of RNA. In eukaryotes, usually about 10 nucleotides long. -Synthesis of these is catalyzed by RNA primase. -When RNA primers are in place, DNA polymerase syntesize new complementary DNA strands along the template strand. -polymerase only works in 5' to 3' direction-problem. -one strand is synthesized continuously, called the leading strand. The other strand is called the lagging strand and is not synthesized continuously. -lagging strand- formed as a series of fragments called Okazi fragments- 1000 to 2000 mucleotides long in prok. and 100 to 200 in euk. -DNA ligase connects the newly synthesized DNA segment to the growing DNA strand by catalyzing the condensation reaction that bonds adjacent phosphate and sugar groups. á in eukaryotes, replication is initiated at many points.
2.6 and 8.3 Transcription and Translation ----------
RNA- almost the same as a DNA strand, except that it is only one strand, and that the nitrogenous base uracil replaces the DNA base thymine. This base also pairs with adenine. it is also much shorter and is composed of a ribose sugar instead of a deoxyribose sugar.
mRNA- copies of DNA sequences. Acts as a messenger. Consists of triplet nucleotide sequences called codons: each codon codes for one specific amino acid. Each mRNA codes for one polypeptide.
tRNA- 75-85 nucleotides in length, about 20 different kinds. Most importantly it has two attachment sites: one of these is the anticodon. This is a nucleotide sequence that binds to the codon of mRNA. the other attachment site is for an amino acid that the mRNA's codon that binds to the tRNA's anticodon codes for.
rRNA- A major component of ribosomes: about two thirds of the ribosome is rRNA.
Transcription- RNA polymerase moves in the 3' to 5' direction of a DNA strand and synthesizes a new complementary strand of nucleotides- in this case ribonucleotides in a 5' to 3' end. So the mRNA strand is antiparallel from the DNA strand from which it is transcribed. When a terminator sequence is reached the mRNA strand is released. ATP provides the energy for transcription.
Introns and Exons- introns are intervening sequences and exons are the protein genes. After transcription the introns are snipped out of the mRNA strands and only the exons remain. This is called splicing.
Retroviruses- contain only RNA and some enzymes. The enzyme reverse transcriptase is used to change RNA into DNA once the virus has invaded the host cell.
HIV-virus- a retrovirus. It uses reverse transcriptase to make DNA, then inserts this DNA into the host cell's DNA. The host cell then produces many copies of the HIV virus.
Reverse transcriptase- why useful? It can change mature mRNA for a specific protein such as insulin into DNA, which can then be spliced into host cell DNA such as E coli without the introns.
Genetic code- There has to be some way for 4 nucleotides to code for all the proteins in some way. The way in which the genetic code works is that each group of three nucleotides stands for one amino acid in a polypeptide chain. 1 triplet=1 amino acid
Translation- Initiation- a smaller ribosomal subunit attaches to a strand of mRNA near its 5' end, exposing its first, or initiator, codon. This is AUG. then a tRNA with the anticodon that is complementary to this codon pairs with it. It carries the amino acid fMet. This is called the initiator complex. Next a larger ribosomal subunit attaches to the smaller subunit and the initiator tRNA becomes locked into the P (peptide) site of the larger unit. The energy for this step is provided by the hydrolysis of guanosine triphosphate (GTP) Elongation- the second codon of the mRNA is positioned opposite the A (aminoacyl) site of the large subunit. a tRNA with an anticodon complementary to the second mRNA codon plugs into the mRNA molecule and, with its amino acid, occupies the A site of the ribosome. When both the P and A sites are occupied, peptidyl transferase forges a peptide bond between the two amino acids. The first tRNA is released and the mRNA scoots down one, the second tRNA goes to the P site, and a new tRNA goes into the A site. This is repeated until an end signal is reached. termination- UAG, UAA, UGA. once one of these is reached, the mRNA strand, the polypeptide and the tRNA's are released.
polysome- A group of ribosomes reading the same mRNA molecule
Ribosomes- eukaryotes contain 80s ribosomes while prokaryotes, mitochondria and chloroplasts have 70s ribosomes.
Free ribosomes- synthesize proteins for use primarily within the cell itself and bound ribosomes synthesize proteins primarily for secretion and lysosomes.
Degeneracy- refers to the fact that there are 61 possible combinations for 20 amino acids and that there must be more than one codon for many of the amino acids.
universal- the genetic code is used in every living organism.
Lac Operon- an operon comprises the promoter, the structural genes, and another DNA sequence known as the operator. The operator is located between the promoter and the structural gene or genes; the operator may overlap the promor, the adjacent structural gene, or both. Transcription also depends on a gene called the regulator, which can be anywhere on the chromosome. It codes for a protein called the repressor, which binds to the operator. When the repressor is bound to the operator, it obstructs the promoter. And then RNA polymerase either cannot bind to the DNA molecule or, if bound, cannot begin its movement along the molecule. No transcription!! This only takes place in prokaryotes.
2.7 Genetic engineering, DNA fingerprinting, gene therapy ----------
Gene transfer- The use of E. Coli in gene technology is well documented. Most of its DNA is in one circular chromosome but it also has plasmids (smaller circles of DNA helix). These plasmids can be removed and cleaved by restriction enzymes at target sequences. DNA fragments from another organism can also be cleaved by the same restriction enzyme and these pieces can be added to the open plasmid and spliced together by ligase. The recombinant plasmids formed can be inserted into new host cells and cloned.
Genetic engineering in agriculture and/or pharmacy- improved crops and animal breeds by increased disease resistance, heavy metal intolerance and better yield. Bacteria can be made to manufacture useful compounds for various purposes, like insulin.
dangers- Some gene transfers are regarded as harmful. Also there might be a possible problem with the release of genetically engineered organisms in the environment. They could spread and compete with the naturally occurring varieties.
PCR- polymerase chain reaction copies and amplifies minute quantities of nucleic acid.
Gel electrophoresis- involves the separation of fragmented pieces of DNA according to their charge and size. Used in DNA profiling.
DNA profiling- useful in some criminal investigation such as murder or rape, or paternity suits. Also the identification of people that died a long time ago, or information about them is possible.
Gene therapy- white blood cells or bone marrow cells are removed and, by means of a vector, the normal gene is introduced and inserted into the chromosome. The cells are replaced in the patient so that the normal gene can be expressed. Examples are the use in cystic fibrosis and SCID. A cure for thalassaemia is also possible.
8.5 proteins ----------
Four levels of structure
Primary- the linear sequence of amino acids, which is dictated by the hereditary information in the cell for that particular protein. Linear sequence of amino acids with peptide linkages
Secondary- The formation of the alpha-helix and beta-pleated sheets, held together by hydrogen bonds.
Tertiary- a complex structure, usually globular, resulting from further folding of the secondary structure of protein; forms spontaneously due to attractions and repulsions among amino acids with different charges on their R groups.
Quaternary- the overall structure of a globular protein molecule that consists of two or more polypeptide chains.
Fibrous proteins- insoluble structural protein in which the polypeptide chain is coiled along one dimension. Fibrous proteins constitute the main structural elements of many animal tissues. ex: collagen, keratin, elastin
Globular- a polypeptide protein folded into a roughly spherical shape. ex: enzymes, antibodies. Usually pretty big proteins.
Polar and non-polar amino acids- There are only 20 different amino acids, and the only differences between them lie in their side (-R) groups. In eight of the molecules, the side group consists of short chains or rings of carbon and hydrogen atoms; as you would expect, such groups are nonpolar and thus hydrophobic. The side groups in seven of the amino acids have polar regions; in acid or basic solution, these regions can become charged. The remaining five amino acids have side groups that are either weak acids or weak bases.
Six functions of Proteins 1) structural- collagen 2) immunoglobulins- antibodies 3) transport- hemoglobin 4) membrane proteins 5) enzymes 6) hormones- insulin
Topic 3 and 10: Genetics
3.1: Chromosomes, genes and alleles ----------
Chromosomes- in eukaryotes, made up of DNA and proteins (histones). They can be stained to show banding- the chromosome structure and banding can be used to arrange the chromosomes in their pairs.
Karyotyping- the general appearance of the chromosomes of an organism with regard to size, number, and shape. Some abnormalities can be detected in the karyotype such as down's syndrome.
Gene- a unit of heredity in the chromosome; a sequence ofnucleotides in a DNA molecule that performs a specific function, such as coding for an RNA molecule or a polypeptide.
Allele-a different form of a gene. For each gene, there are two alleles found in the chromosomes.
Genome- a complete set of chromosomes, with their associated genes.
3.2 Gene mutation ----------
gene mutation- the change of a gene from one allelic form to another; an inheritable change in the DNA sequence of a chromosome.
insertion and deletion- the difference is that an insertion is when a nucleotide or nucleotide sequence is inserted into the DNA strand, whereas a deletion is when a nucleotide or nucleotide sequence is deleted from the DNA strand.
base substitution mutation- normal hemoglobin contains glutamic acid at a specific position. Sickle cell anemia hemoglobin contains valine at the same position. The difference between these two amino acids is only one nucleotide. There are 450 nucleotides for hemoglobin, and a matter of life and death can be traced to one 'misprint' in over 450 nucleotides.
3.3 and 10.1 Meiosis ----------
Meiosis- the two successive nuclear divisions in which a single diploid cell forms four haploid nuclei, and segregation, crossing over, and reassortment of the alleles occur; gametes or spores may be produced as a result of meiosis.
homologous chromosomes- chromosomes that carry corresponding genes and associate in pairs in the first stage of meiosis; each member of the pair is derived from a different parent.
Process of Meiosis
Interphase- the chromosomes are replicated, so that by the beginning of meiosis each chromosome consists of two identical sister chromatids held together at the centromere region.
Prophase 1- the chromatin condenses and the chromosomes come into view. The homologous chromosomes come together in pairs. Then synapsis occurs. the paired chromosomes are called a tetrad. They then cross over- this is the exchange of segments of one chromosome with corresponding segments from its homologous chromosome. This occurs at points called chiasmata. Spindle microtubules begin to form around the cell. The nucleoli and the nuclear envelope dissapear.
Metaphase 1- the homologous pairs line up along the equatorial plane of the cell. The centromere region of each homologue has doubled by the end of metaphase, and spindle fibers have become associated with the kinetochores. Random orientation- increases genetic variety and takes place in this stage.
Anaphase 1- The homologues each consisting of two sister chromatids, separate, as if pulled apart.
Telophase 1- The homologues have moved to the poles.
Interphase 2- this may or may not occur in some species.
Prophase 2- new spindle fibers begin to form.
Metaphase 2- the chromatid pairs in each nucleus line up on the equatorial plane. Spindle fibers are once again associated with the kinetochores, and other spindle fibers extend from the poles.
Anaphase 2- the sister chromatids separate from one another. Each chromatid moves toward one of the poles.
Telophase 2- The spindle microtubules dissapear and a nuclear envelope forms around each set of chromosomes. Ther are now four nuclei in all, each containing the haploid number of chromosomes.
non-disjunction- when homologous chromosomes or their chromatids may not separate.
Down's syndrome- when an individual has three, rather than two copies of chromosome 21. This is usually because of non-disjunction of the parental gamete, resulting in 47 chromosomes, with an extra copy of chromosome 21 in the cells of the affected individual.
Mendel's law of segregation- every individual carries pairs of factors for each trait and the members of the pair segregate during the formation of gametes.
Mendel's law of independent assortment- when gametes are formed the alleles of a gene for one trait segregate independentrly of the alleles of a gene for another trait.
Recombination- the formation of new gene combinations; in eukaryotes, may be accomplished by new associations of chromosomes produced during sexual reproduction or crossing over; in prokaryotes, may be accomplished through transformation, conjugation or transduction
3.4 Theoretical genetics ----------
Genotype- the genetic constitution of an individual cell or organism with reference to a single trait or a set of traits; the sum total of all the genes present in an individual.
Phenotype- observable characteristics of an organism, resulting from interactions between the genotype and the environment.
Dominant allele- an allele whose phenotypic effect is the same in both the heterozygous and homozygous conditions. It is always expressed.
Recessive allele- an allele whose phenotypic effect is masked in the heterozygote by that of another dominant allele.
Codominant allele- an allele that, when it is heterozygote, it expresses its homozygous phenotype simultaneously with the other allele- an example is the human blood type AB.
Locus- in genetics, the position of a gene in a chromosome. For any given locus, there may be a number of possible alleles.
Homozygous- when a diploid organism carries identical alleles at one or more genetic loci- identical alleles for a specific gene.
Heterozygous- when a diploid organism carries two different alleles at one or more genetic loci.
Carrier- when a person is heterozygous for a specific trait and the recessive trait is not expressed, but still in the person's genes so that it may be passed on to the next generation.
Test cross- a mating between a phenotypically dominat indicidual and a homozygous recessive 'tester' to determine the genetic constitution of the dominant phenotype, that is, whether it is homozygous or heterozygous for the relevant gene. Multiple alleles- genes that have more than two alleles.
Human blood type- there are three alleles for blood type: A, B and O. A and B are codominant and O is recessive. Thus, an individual with blood type A has to have either two A alleles or an A and an O allele. Their red blood cells bear the A antigen and their blood plasma contains B antibodies. An individual with blood type B bears the B antigen and has A antibodies. Individuals with AB blood type have both antigens but no antibodies. Individuals with blood type O have no antigens but both antibodies.
Sex chromosomes- For one pair of chromosomes, male and female chromosomes are different. Females contain two X chromosomes and males contain an X chromosome and a Y chromosome. Thus, a female will contribute an X chromosome, and the male will contribute either an X or a Y chromosome. Some genes are present on the X chromosome and absent from the shorter Y chromosome in humans. This is sex-linked.
Sex linkage- an inherited trait, such as color discrimination, determined by a gene located on a sex chromosome and that therefore shows a different pattern of inheritance in males and females. Two examples- hemophilia, eye color in drosophilia. Most sex-linked traits are found on the X chromosome- which means that for these traits, a female can be either homozygous or heterozygous, while a male can either have it or not- only one recessive X allele and a Y chromosome, and that means that the male has that sex-linked trait. Female carriers are heterozygous for X-linked alleles.
Examples of the above- phenotypic and genotypic ratios
3.5 Applied Genetics ----------
Genetic screening- seeing what the genetic makeup is of an individual. Advantages- Pre-natal diagnosis of genetic diseases, immigration disputes, confirming animal pedigrees.
Human Genome Project- an international cooperative venture to sequence the complete human genome. It should lead to an understanding of many genetic diseases, to genome libraries and the production of gene probes to detect sufferers and carriers of genetic diseases. Such as Duchenne muscular dystrophy. It also leads to the production of pharmaceuticals based on DNA sequences.
Clone-a line of cells, all of which have arisen from the same single cell by repeated cell divisions; a population of individuals derived by asexual reproduction from a single ancestor.
Example- early divisions of a fertilised egg produce 8 cells each of which could give rise to an embryo. After in vitro processes the 8 resultant separated embryos can be transferred to surrogate mothers to continue using selected prime animals for the production of more gametes. At present it is used for cloning genetically manipulated animals to produce pharmaceutical biochemicals.
Cloning- cloning happens normally- monozygotic twins. Some may regard the in vitro production of two embryos from one to be acceptable-others would see this as leading to the selection of those 'fit to be cloned' and visions of 'eugenics and super-race'.
Breeding- selectively choosing those who have a good phenotype to make a particular animal or plant. Such as dogs- and domesticated animals. Also plants have been selectively bred for disease resistance, increased food production, high yield of milk/wool/protein etc, breeding plants to select those that can spread to extend the range of species.
10.2 Dihybrid crosses ----------
- autosomal genes- genes other than sex-linked.. so not on X or Y chromosome.
Dihybrid cross
AaBb x AaBb A: tall a: short B:black b:white AB Ab aB ab AB AABB AABb AaBB AaBb Ab AABb AAbb AaBb Aabb aB AaBB AaBb aaBB aaBb ab AaBb Aabb aaBb aabb
genotypic ratios 4 AaBb 2 AaBB 2 Aabb 2 AABb 2 aaBb 1 AABB 1 AAbb 1 aaBB 1 aabb
- trick of the trade: all heterozygous- out of 16 there will be 4 individuals.
only one allele-set heterozygous- out of 16 there will be 2 individuals all alleles homozygous- only one kind.
Phenotypic ratios 9:3:3:1 9 tall black 3 tall white- recombinant 3 short black-recombinant 1 short white-recombinant
another look at recombinants- If you cross a tall, white (Ttrr) with short, red (ttRr) then in the F1 generation there will be 4 different phenotypes: tall white, short red, tall red, and short white. Well then! the tall red and short white are recombinants because neither parent had this combination.
10.3 Autosomal gene linkage and gene mapping ----------
Autosomes- any chromosome that does not have a role in determing the sex of the individual- so for the human any of the 22 non-sex chromosomes.
linkage group- a pair of homologous chromosomes; genes that tend to stay together because they aare on the same pair of homologous chromosomes are said to be linked or in the same linkage group. While mendel said that all alleles segregate independently, its not really true. Because the genes that are on the same chromosome, for example, the genes for tallness and freckles, will stay together if they are on the same chromosome. So they are linked. TF
tf
is how it would be written: the two lines show that they are on different chromosomes, get it? Most likely, they will stay together forever. Or something like that. How to cross them- I think you just do it the same as any other dihybrid cross. So the above example=TtFf, and just do TtFf times TtFf. The recombinants would be Ttff and ttFf, because those are tall and non-freckled and short and freckled, a combination which neither parent is.
10.4 statistical analysis ----------
10.5 polygenic inheritance ----------
Analyse both monohybrid and dihybrid genetic crosses using the chi-squared test
O=observed number n=number of different classes E=expected number degrees of freedom= n-1
polygenic inheritance- the determination of a given characteristic, such as weight or height, by the interaction of many genes. Human skin color is believed to be controlled by 3 or 4 different genes.
interaction between genes- this can cause modified mendelian ratios in dihybrid crosses. Few phenotypes result from the action of one gene. Most are due to a sequence of two or more genes, and thus the action of a gene earlier in the sequence can effect a gene later in the sequence. This is the basis of epistasis.
10.6 Applications of genetics to agriculture and horticulture ----------
Inbreeding- the mating of individuals that are closely related genetically.
outbreeding- the mating of individuals that are not closely related genetically and form new combinations of genes.
interspecific hybridisation-
polyploidy- when a cell contains more than two complete sets of chromosomes per nucleus.
F1 hybrid vigour- In the 1950s scientists demonstrated that by mating two breeds, called crossbreeding, offspring with heterosis, or hybrid vigor, were produced. This means that the calves outperform their parents for health, growth rate, and prolificacy, or ability to produce offspring. Crossbreeding increases the total pounds of beef produced by 8 to 20 percent. In the dairy industry, crossbreeding results in somewhat less heterosis than when beef breeds are crossed.
Transgenic techniques in agriculture and/or horticulture- Transfer of human copy DNA into bacteria, eg human genes for insulin and factor VIII. Emphysema drug genes into sheep, expressed as protein in milk. Winter flounder fish gene to make tomatoes frost resistant. Most groups have no ethical objections to the use of foods containng copy DNA of human origin. However it is a very sensitive issue.
Biodiversity- Wild plants as well as ancient farm breeds need to maintain biodiversity. This is because their alleles may have future value- cure for new disease, etc.
Topic 4: Ecology
4.1 communities and ecosystems ----------
Ecology- The study of the interractions of organisms with their physical environment and with each other and of the results of such interactions.
Ecosystem- The organisms in a community plus the associated abiotic factors with which they interact.
population- any group of individuals of one species that occupy a given area at the same time; in genetic terms, an interbreeding group of organisms.
community- all the populations of organisms inhabititing a common environment and interacting with one another.
Species- a group of organisms that actually interbreed in nature and are reproductively isolated from all other such groups; a taxonomic grouping of anatomically similar individuals.
habitat- the place in which individuals of a particualr species can usually be found.
Biosphere- the zones of air, land and water at the surface of the earch occupied by living things; hence, all the places in which organisms can live on earth.
Food Chain- a sequence of organisms related to one another as prey and predator.
Food Web- linked food chains with many brances and interconnections.
Trophic level- the series of feeding level producer- plants Primary consumer- organism that eats plants secondary consumer- organism that eats other consumers. Autotroph- an organism that is able to synthesize all needed organic molecules from simple inorganic substances and some energy sources.
Heterotroph- an organism that must feed on organic materials fromed by other organisms in order to obtain energy and small building-block molecules; in contrast to autotrophs.
Detritivore- organisms that live on dead and discarded organic matter; include large scabengers, smaller animals such as earthwoms and some insects, as well as decomposers.
Saprotroph- an organism that feeds on nonliving organic matter.
4.2 Photosynthesis, respiration and energy relationships ----------
light- the initial energy source for almost all communities.
photosynthesis- light energy is converted into chemical energy. Light +H2O +CO2= glucose, oxygen, and H2O.--- light energy is used to split water molecules to produce oxygen, hydrogen, and to produce ATP. ATP and hydrogen are used to fix carbon dioxide to make organic molecules. It can be monitored by the production of oxygen, the uptake of carbon dioxide, or the increase in biomass.
Chlorophyll and light waves- chloroplasts contain both chlorophyll a and chlorophyll b. chlorophyll a is the pigment directly involved in the transformation of light energy to cheimical energy. chlorophyll b-carotenoids. They both absorb blue light the most, and then orange-red.
temperature on photosynthesis- there are two different reactions, one which is temperature-independent and one which is temperature dependant. The temperature-dependent reactions increased in rate as the temperature was increaed, but only up to about 30 degrees celsius, after which the rate begins to decrease. These reactions are controlled by enzymes- they break down.
light intensity- as light intensity increases, so does the relative rate of photosyntesis- to a certain point. Then the curve levels out.
carbon dioxide- same as for the light intensity condition. Probably the chloroplasts can't do any more work anyways.
respiration- involves the breakdown of organic molecules to release energy stored by photosynthesis. The carbon dioxide fixed by photosynthesis is released by respiration. The energy released during repiration of complex compounds in an organism is used within an organism to do work or is lost as heat.
Biomass-total weight of all organisms living in a particular habitat or place. Measuring the increase in biomass gives us a measurement of net productivity- the net profit. As an organism grows its biomass increases.
um, cool fact? when energy transformations take place, including those in living organisms, the process is never 100% efficient, commonly being only 10-20%.
pyramid of energy- only about 10% of all energy from one organism is passed to the other. What happens to all the other energy?? It is used metabolically and lost as heat.
another cool fact- energy enters and leaves an ecosystem, but nutreints must be recycled.
4.3 populations, natural selection, and evolution ----------
population size- affected by natality, immigration, mortality and emigration. natality and immigration increase it, mortality and emmigration decrease it.
exponential growth phase- the growth rate of the population increases markedly over time. It shoots up very rapidly as the number of reproducing individuals increases with each generation. The more you have, the more you get.
plateau phase- the population has reached the carrying capacity- that is, the number of individuals that the environment can support under a particular set of conditions.
transitional phase between latter phases- the growth rate slows down but there are still fluctuations. Eventually the population will stabilize.
carrying capacity- The number of individuals of the population that the environment can support given a particular set of conditions.
Evolution in brief- populations tend to produce more offspring than the environment can support. Part of evolution. Because of this, there is competition for survival- since there is not enough for everybody to go around. All offspring are different in some way, those with the best variations for the environment will survive, and breed, and pass on their traits to their offspring. This is called natural selection- it is how species evolve so that they are best adapted to their environment. Evolution is a response to environmental change- you need new adaptions.
4.4 Human impact ----------
Greenhouse effect- Because of increased human activities, the ozone layer is thinning. Gases released into the atmosphere by humans such as chlorofluorocarbons from refrigerators, etc. This reacts with the ozone molecule- the choline molecule that is chipped of chlorofluorocarbons, that is. This is thinning out the ozone layer. One impact this has is that the earth is becoming much hotter- the ice caps are melting and the water level is rising, and the temperatures are rising too. Also there is increased risk of cancer.
Increase of human habitat- as the human population continues to grow their habitat is increasing also. As a result many of the earth's forests are being cut down, so that many organisms have no home. etc.
4.5 Ecological techniques ----------
Random sample- each individual has an equal chance at being picked.
capture-mark-release-recapture method- a random sample of organisms from a specific habitat is picked- for example 20 beatles. They are all marked and put back into their environment. A specified time later another sample of beatles are taken, this time 30.You check how many of those are marked. In this case there are 5 To see what the population is using these numbers use the following formula:
(N1*N2)/N3 where N1=number initially caught, marked and released N2=total number of individuals caught in the second sample N3=number of marked individuals in the second sample.
thus, the population is 20*30/5 which is 300 total beatles.
Quadrants- a habitat in which a particular population is found is divided up into quadrants- all equal in size. For example, if you divide the population into 100 quadrants, you then take the population of 10% of the total population- thus, 10 of the quadrants. The population of these is taken and multiplied by 10 to estimate the total population.
mean- the total sum of numbers divided by the number of data.
mode- the most recurring number in the set of data.
median- when all numbers are put in order, the middle number.
standard deviation- used to summarise the spread of variables around the mean. 68% of the values fall within one standard deviation of the mean (minus and plus). a small standard deviation indicates that the data is clustered closely around the mean value. A larde sd means a wider spread around the mean. The closer the means and the sd of data the more likely the samples are drawn from a similar (the same) population.
Topic 5 and Option H:Human Physiology Topic 11: Human Reproduction Topic 12: Defence Topic 15: Excretion
Digestion and Nutrition ----------
Digestion- the breakdown of ingested food materials into molecules that can be delivered to and utilized by the individual cells of the animal body. Why important? the molecules serve a variety of functions. They may be energy sources, they may provide essential chemical elements, such as calcium, nitrogen or iron, or they may be molecules that cells need but cannot synthesize for themselves, such as certain amino acids, fatty acids, and vitamins.
Enzymes- play an important role in the digestion of nutrients. Responsible for the breakdown of food into molecules that can be used by the body.
Secretion- under both nervous and hormonal control. Hormonal controls include the hormones gastrin and secretin. Gastrin stimulates the secretin of gastric juices and muscular contractions of stomach and the intestine, and is secreted by the stomach. Secretin is releases by the duodenum of the small intestine and stimulates the secretion of alkaline pancreatic fluids and bile.
Proteases- enzymes responsible for the breakdown of proteins. An important one- Pepsin. Formed in the chief cells of the gastric pits of the stomach. These cells release pepsinogen. Hydrochloric acid initiates the conversion of pepsinogen to its active form, pepsin, by splitting off a small portion of the molecule. Once pepsin is formed, it acts on other molecules of pepsinogen to form more pepsin. Pepsin breaks proteins down into peptides. It's optimum pH is between 1.5 and 2.5, the pH of the stomach. The enzymes pepsin and trypsin are both initially synthesized as inactive precursors and are subsequently activated- trypsin is first released as chymotrypsin and is activated by the duodenal enzyme enterokinase is mixed with it. This is because both of these enzymes are very strong- only in the presence of protein are they allowed to do their work.
Lipase- enzymes that break down lipids into usable forms. Its source is the pancreas, its substrate is fats, and its site of action is the small intestine, where its optimum pH is around 7 and 8. They hydrolyze fats into glycerol and fatty acids.
amylase- these enzymes break down sugars. There are two different kinds; salivary amylase, pancreatic amylase. Pancreatic amylase is, as its name suggests produced in the pancreas. However its site of action is in the small intestine. It breaks down starches into disaccharides. its optimum pH is around 7 and 8.
Digestive juices- these help in the digestion of food. They are secreted into the alimentary canal by glands including salivary, stomach wall, pancreas, and wall of small intestine. Saliva contains mucus, which lubricates the food so that it can be swallowed easily. It also contains sodium bicarbonate which makes it slightly alkaline. Gastric juices, which are secreted by the gastric pits (the chief cells and the parietal cells which secrete pepsinogen and hydrochloric acid, respectively) contain the aforementioned. HCI is extremely acidic, and that is why the pH of the gastric juices is between 1.5 and 2.5. Also gastric juices contain mucus. The pancreatic juices contain an alkaline fluid, which neutralizes the stomach acid. It also contains a number of digestive enzymes such as pancreatic amylase, lipase, trypsin, chymotrypsin, carboxypeptidase, and deoxyribonuclease.
exocrine glands- Exocrine glands secrete either directly or by ducts onto a surface. Sweat, salivary, lacrimal (tear), and intestinal glands are exocrine glands.
Explanation of structural features- The tight junctions and desmosomes bind these cells together in a continuous sheet. Microvilli on the surface of the epithelial cells greatly increase the absorptive surface of the interstine. They also contain digestive enzymes which are part of the cell membrane, and proteins involved in the transport of nutrient molecules across the cell membrane. They contain numerous mitochondria because they have high energy requirements- due to the active transport.
Digestion of starch- the breakdown of starch begins in the mouth, where the enzyme salivary amylase acts on it and turns it into maltose. Probably this is only to make the taste of starch better. The food then moves down the esophagus into the stomach. Starch and sugar are held in the stomach for a short time only, usually no more than one to two hours. In the small intestine, pancreatic amylases continue the breakdown of starch begun in the mouth, producing disaccharides. Other enzymes break different disaccharides down into monosaccharides. These include maltase (maltose) lactase (lactose) and sucrase (sucrose).
Absorption- the movement of water and dissolved substances into a cell, tissue and organism. In this context it refers to the movement of nutrients and products of digestion into the villi of the large intestine. Absorption is carried out by the epithelial cells of the intestinal mucosa.
Balanced Diet- The energy requirements of the body can be met by the ingestion of carbohydrates, proteins, or fats. Energy requirements are ordinarily met by a combination of the three. carbohydrates and proteins supply about the same number of calories per gram of dry weight, fats supply about twice as much as either of them. Also the cells of the body need the 20 different kinds of amino acids. Humans can synthesize about 12 of them. The other eight are known as the essential amino acids. Plants are the ultimate source of these. Humans also require polyunsaturated fats that provide fatty acids needed for the synthesis of fats and a group of hormone-like compounds known as prostaglandins. These can be obtained by eating plants or insects. or animals that have already eaten these. Also vitamins are essential to the human body. They function as coenzymes. There are many different types and they are found in all kinds of different sources. Also the body needs many different kinds of inorganic substances, or minerals. These include calcium and phosporus for bone formation, iodine for thyroid hormone, and so on.
Malnutrition- Malnutrition is the imbalance between the body's demand for nutrients and the available supply of nutrients. Malnutrition can result from an unsatisfactory diet or from a disorder that interferes with the body's use of food. Obesity, or the state of being excessively fat, is a form of malnutrition that contributes to many health problems. It may be defined as body weight more than 20 percent above a person's ideal weight. Anorexia nervosa is a condition characterized by extreme weight loss. Nervosa means the nerves, or neurotic. This life-threatening disease usually occurs in young women. It requires professional treatment.
Cellulose- undigestible by humans; can be digested by herbivores, such as cows and horses, because they retain it long enough for digestion by microorganisms present in their digestive systems.
Lipids- lipid molecules tend to 'unite' or coalesce and are only accessible to lipase at the lipid-water interface- because lipids are hydrophobic. Therefore, lipase, the enzyme which breaks down lipids, needs to have an active site to which a hydrophobic substrate binds. Bile solves this problem. Bile molecules have a hydrophillic end and a lipophillic end and thus prevent lipid droplets coalescing with each other.
Ileum- uses facilitated diffusion, active transport and endocytosis to absorb and transport food.
Unabsorbed materials- The body does not absorb cellulose and lignin, which cannot be digested by the body, and bile pigments, bacteria and intestinal cells, because they are not needed by the body in any way and may even harm the body. They are all egested.
The transport system ----------
The heart- Its walls are made up predominantly of a specialized type of muscle-cardiac muscle. Blood returning from the body tissues enters the right atrium through two large veins, the superior and inferior vena cava. Blood returning from the lungs enters the left atrium through the pulmonary veins. The atria, which are thin-walled compared to the ventricles, expand as they receive the blood. both atria then contract simultaneously, assisting the flow of blood through open valves into the ventricles. Then the ventricles contract simultaneously; the valves between the atria and ventricles are closed by the pressure of the blood in the ventricles. The right ventricle propels deoxygenated blood into the lungs through the pulmonary arteries; the left ventricle propels oxygenated blood into the aorta, from which It travels to the other body tissues. Valves between the ventricles and the pulmonary artery and the aorta close after the ventricles contract, thus preventing backflow of blood.
Heartbeat- the stimulation of cardiac muscle originates in the muscle itself. It is initiated by a special area of the heart, the sinoatrial node, which is located in the right atrium. This region of tissue functions as the pacemaker. It is composed of specialized cardiac muscle cells that can spontaneously initiate their own impulse and contract. >From the pacemaker the impulse spreads throughout the right and left atria. As it passes along the surface of the individual cardiac muscle cells, it activates their contractile machinery, and they contract. The atrioventricular node initiates impulses that are carried by special muscle fibers called the bundle of His to the walls of the right and left ventricles which then contract almost simultaneously. The autonomic nervous system does not initiate the heartbeat but it does modify its rate. Messages to the heart are carried on the vagus nerve. Adrenaline from the adrenal medulla affects the heart in the same way that the sympathetic nerves do.
Cardiac cycle- see heart. The sound of the heartbeat, "lubb-dup, lubb-dup", are the sounds of the valves. The "lubb" is the closing of the valves between the atria and the ventricles, the "dup" sound is the closing of the valves leading from the ventricles to the arteries. Systolic blood pressure refers to the pressure of the blood when the ventricles are contracting, diastolic pressure refers to when the ventricles are relaxed.
Blood vessels- Arteries carry blood away from the heart and have thick walls to resist the pressure of blood inside. It is made up of 3 layers: the tunica intima, which is endothelium and connective tissue, the tunica media, which is the elastic lamella and muscle, and the tunica adventitia, which is the collagen and elastic fibres. Veins are large blood vessels which carry blood toward the heart. Unlike other blood vessels, they have valves to prevent backflow. They have the same layers as the arteries, but does have a weaker tunica media. It does not have as many elastic fibres. The lumen or the center of the vein tends to be larger in diameter than in the equivalent arteries, reflecting a slower rate of flow. Capillaries are the smallest and most numerous blood vessels, having an average diameter of 8 micrometers and a wall thickness of only .2 micrometers. They are the most important part of the circulation for they are the site of exchange with tissue cells. They are made up of endothelium cells only.
Blood- composed of plasma, erythrocytes (red blood cells), leucocytes (white blood cells) and platelets.The leucocytes and platelets form only about 1% of the blood volume. The erythrocytes form about 44% of the blood volume, and the other 55% is blood plasma. The blood transports the following: heat, nutrients, oxygen, carbon dioxide, hormones, antibodies, and waste products.
Diseases of the heart ----------
Artherosclerosis contributes to both heart attacks and strokes. In this disease, the linings of the arteries thicken due to the accumulation of abnormal smooth muscle cells, and their inner surfaces become roughened by deposits of cholesterol, (Low-Density lipoproteins, LDL's)fibrin, and cellular debris. Such arteries, becoming inelastic, no longer expand and contract, and blood moves with increasing difficulty through the narrowed vessels. Thrombi (blood clots) and emboli thus form more easily and are more likely to block the vessel.
Coronary thrombosis is the result of a blood clot called a thrombin. These form in the blood vessels of the heart itself or elsewhere in the body and travels to the heart and lodges in a vessel there. The blood clots cut off the oxygen supply to the heart, the cardiac muscle cells may die. This leads to a heart attack.
Factors- Having parents with heart attacks, since it may be genetic, old age, being male, smoking, obesity, eating too much saturated fat and cholesterol, lack of exercise.
Lymphatic system ----------
How lymph is formed- Plasma proteins maintain the high osmotic potential of the blood in relation to the interstitial fluid and thus in preventing excessive loss of fluid from the blood. At the arteriole end of the capillaries, the pressure of the circulating blood, the hydrostatic pressure, is greater than the osmotic potential, which forces some of the watery component of blood to leave capillaries along with nutreint molecules and oxygen. The fluids lost from the blood to the tissues are collected by the lymphatic system, which routes them back to the bloodstream. Lymph also contains fats as lymph is the medium in which fats absorbed from the digestive tract are returned to the bloodstream.
Transport functions- transports fluids back to the bloodstream, and fats that are absorbed from the digestive tract back to the bloodstream. They also contain specialized white blood cells that are the effectors of the immune response
Defence against infectious disease ----------
Disease-caused by a variety of organisms- bacteria, fungi, viruses, etc
Pathogen- anything which can cause disease in an organism. Virus- HIV virus which causes AIDS, also smallpox Bacteria- meningitis- an infection of the membranes covering the brain and spinal chord. Pneumonia. Fungi-One serious fungus-caused disease that may attack people and animals is ergotism. The fungus ergot develops on grasses, especially on rye. It contains a number of poisons called alkaloids. If the grain is harvested and the ergot is not removed, it will get into bread made from the rye and cause ergotism also known as St. Anthony's fire for which there is no known cure. The disease may also infect cattle that eat the rye grains left in a field. protozoa-African sleeping sickness- cuased by trypanosoma rhodesiense. flatworms-Tapeworms attach to the intestinal wall by means of hooks or suckers located on their heads and absorb nutrients across their cell walls directly from the host's food as it passes through the intestine. Roundworms cause many human diseases, including hookworm and pinworm diseases, elephantiasis, and trichinosis, which can be acquired by eating insufficiently cooked pork or other meats.
Anatomic bariers-the body's first line of defense against foreign invaders is its outer wrapping of skin and mucous membranes. the skin, with its tough layer of keratin, is an impregnable barrier as long as it is intact. When it is not, large numbers of microorganisms gain ready entry to the body. The epithelium that forms mucous membranes is more fragile than the skin, but it is constantly flushed with fluids, such as mucus, saliva and tears, that contain antimicrobial substances. The epithelium lining of the respiratory tract is carpeted with cilia, which sweep away inhaled organisms, dirt and debris trapped in the protective layer of mucous.
Antigen- a foreign substance, usually a protein or polysaccharide, that when bound to a complementary antibody displayed on the surface of a B lymphocyte or to a complementary T-cell receptor, stimulates an immune response.
Antibody- a globular protein, synthesized by a B lymphocyte, that is complementary to a foreign substance (antigen) with which it combines specifically.
methods by which pathogens gain entry into the body Pathogenic organisms can enter the body in various ways. Some such as those that cause the common cold, pneumonia, and tuberculosis are breathed in. Others such as those that cause venereal diseases enter through sexual contact of human bodies. Still others such as those that cause bacillary dysentery, cholera, and typhoid fever get in the body through contaminated food, water, or utensils. Insects can spread disease by acting as vectors, or carriers. Flies can carry germs from human waste or other tainted materials to food and beverages. Germs may also enter the body through the bite of a mosquito, louse, or other insect vector. 1) through a cut or break in the mucous membranes or the skin 2) tissue transplants from an infected person Some bacterial diseases
Diphtheria, acute bacterial infection with symptoms of sore throat, fever, rapid pulse, and swollen neck glands. Mass immunization has made the disease extremely rare in developed countries. However, it is still a hazard to nonimmunized people in poor, developing countries. The Corynebacterium diphtheriae bacterium has an incubation period of two to five days and may be carried on the skin or in the nose of a person immune to the disease. Once it is passed on to a nonimmune person, the bacterium may multiply in the throat and create a membrane that spreads over the surrounding areas of the throat and cause breathing difficulties. When the infection is confined to the skin, it causes minor yellow spots or sores. Life-threatening complications may arise when the bacterium releases a toxin into the bloodstream. Other rare complications are paralysis of the throat or limbs, and heart failure.
Tuberculosis (or TB), an infectious disease caused in humans by the bacterium Mycobacterium tuberculosis. Tuberculosis is characterized by a lifelong balance between the host and rod-shaped bacteria. It usually is contracted by inhaling infected droplets coughed or sneezed into the air by an infected person. The infection begins in the lungs. In most cases, the immune system attacks the infection and healing occurs, leaving a scar on the lungs. In about 5 percent of the cases the infection spreads, first to the lymph nodes connected to the lungs and then, via the bloodstream, to other organs in the body. This stage is called miliary tuberculosis, and it may be fatal. In some instances, the disease does not affect the lungs at all, but may involve lymph nodes or other parts of the body. This type of infection is common to bovine tuberculosis, or M. bovis, which is transmitted to humans by contaminated cow's milk and is extrememly rare in developed countries.
AIDS The disease known as AIDS is a complicated illness that may involve several phases. It is caused by a virus called HIV that can be passed from person to person. AIDS impairs the human body's immune system the system responsible for warding off disease and leaves the victim susceptible to various infections. The virus enters the bloodstream and destroys certain white blood cells, called T lymphocytes, that play a key role in the functioning of the immune system. The virus can also infect other types of cells in the body, including the immune-system cells known as macrophages. Unlike T lymphocytes, however, macrophages are not killed by the virus. In fact, research has suggested that macrophages may carry the AIDS virus to healthy brain cells, to the lymphatic system, and to other healthy cells in the body. AIDS is transmitted by direct contamination of the bloodstream with body fluids that contain the AIDS virus, particularly blood and semen from an HIV-infected person. The virus is usually transmitted through various forms of sexual intercourse, the transfusion of virus-contaminated blood, or the sharing of HIV-contaminated intravenous needles.
Types of Defence ----------
Blood clotting- This requires platelets and at least 15 factors normally present in the bloodstream or on the cell membranes. The sequence of events starts when plasma encounters a rough surface or a protein molecule known as tissue factor. This is found on the outer surface of many different cell types. When tissue factor reacts with a specific circulating plasma protein chemical reactions are initiated. A molecule called thromboplastin is activated. This molecule acts to convert prothrombin, a plasma protein produced by the liver, to its active form, the enzyme thrombin. Thrombin, in turn, converts fibrinogen, a soluble plasma protein, to fibrin. The fibrin molecules clump together, forming an insoluble network that enmeshes red blood cells and platelets to form a clot. The clot contracts, pulling together the edges of the wound.
Active immunity- When people develop antibodies against a disease by the action of their own immunity system, they have active immunity.
Passive immunity- When they are given someone else's antibodies, however, they just have passive immunity to a disease. Temporary form of immunity.
Natural immunity- includes two parts. One part, called humoral innate immunity, involves a variety of substances found in the humors, or body fluids. These substances interfere with the growth of pathogens or clump them together so that they can be eliminated from the body. The other part, called cellular innate immunity, is carried out by cells called phagocytes that ingest and degrade, or ,pathogens and by so-called natural killer cells that destroy certain cancerous cells. Innate immunity is nonspecific that is, it is not directed against specific invaders but against any pathogens that enter the body.
Artificial immunity- immunity through the use of serums or vaccines
Antibody/Antigen response ----------
This is a very large and complicated response in which B cells, helper t-cells, cytotoxic T-cells memory cells, MHC and immunoglobulins all play a role in. The T-lymphocytes are involved in a cell-mediated response, as opposed to the B-cells, which are involved in antibodies.
There are two different T cells: the helper t cells and the cytotoxic t cells. They are the offspring of self-regenerating stem cells in the marrow of long bones. Primitive versions of these cells then creep into the thymus glands. These are the future T cells. Within the thymus gland the T cells to through the complex process of differentiation, selection, and maturation. Eventually two different types of T cells are the result of this process: the helper t cell and the cytotoxic T cell. The recognition of antigens by the T cells is done with the help of MHC: major histocompatibility complex. This is the protein component of antigens fouind on the body's own cells. Each person has their own type of MHC- it is like a fingerprint. During the selection of T cells, the T cells are exposed to MHC antigens. Those cells that bind optimally to this MHC are the ones selected to complete their development and maturation.
The cell mediated response is as follows.Infection of a eukayotic cell by a foreign microorganism, such as a virus, results in the appearance of new antigens on the surface of that cell. These antigens, which are short peptides derived from the antigens orignally on the suface of the infectious particle, are bound to and displayed on the individuals Class 1 MHC antigens. when a cytotoxic T cell encounters such an MHC antigen and foreign antigen to which its receptor can bind, it differntiates into active cells that attack and lyse the infected cells and into memory cells that remain in the circulation indefinitely. The activated cytotoxic T cell also releases chemicals called lymphokines that attract macrophages and stimulate phagocytosis. When a helper T cell encounters a cell to which it can bind it becomes activated. It then produces proteins called interleukins which act as hormones. They stimulate differentiation and proliferation of both B lymphocytes and cytotoxic T cells following activation. Binding of helper T cell is an essential step in producing plasma cells and memory cells.
B lymphocytes are active in a humoral immune response, which is mediated by antibodies. When a B-lymphocyte meets an antigen complementary to the structure of the antibodies on its surface the B lymphocyte divides and produces a plasma cell and a memory cell. The plasma cell is a specialized antibody factory. It takes 5 days to produce a fully mature synthesizing cell at maximum capacity. A memory cell also produces antibodies but circulates for much longer than a plasma cell- it circulates for long periods of time-up to a lifetime.Antibodies act in three ways: 1)they may coat the foreign particles and cause them to clump together in such a way that they can be taken up by phagocytic cells 2) they may combine with them in such a way that they interfere with some vital activity 3)they may combine with other blood components (known as a complement) actually lyse and destroy foreign cells.
antibodies- consists of 4 subunits, two identical light chains, two identical heavy chains. The light chains have about 214 amino acids each, and the heavy chains have about twice as many. Both the light and the heavy chains have constant (C) regions in which the amino sequence is identical from one molecule to the next. Each type of chain also has a variable V region. Some of the amino sequences are the same, but at approximately 40 positions the amino acids cary from one antibody to another. These amino acid sequences come together to form the two active regions of the molecule, the sites that recognize and bind a specific antigen.
five distinct classes- IgG, IgA, IgD, IgM, IgE. They are distinguished by the constant regions of their heavy chains: each class has a chracteristuic constant region, shared by all members of the class. Detection of HIV antibodies means you have AIDS. For treatment, antibodies is blood and tissue typing for transplant compatibility. IgG-gamma globulin. The principal type of antibodies. IgA-mucosal immunity- found in secretions like tears, saliva, milk. IgD- on the surface of B lymphocytes prior to activation and are the sites at which antigens intially bind to the cell. IgM-also on the surface of B cells are the first to be secreted in te course of infection and last a relatively short time. IgE-plays a major role in the expulsion of parasits, such as worms, from the intestinal tract. Also involved in allergic reactions.
Immunisation- ie. vaccination- Vaccines made with live organisms, such as those against measles, mumps, and rubella, need be given only once to confer lifelong immunity. Vaccines made from inactivated or killed organisms or toxoids, substances from disease-causing organisms that have been treated so as to induce formation of antibodies when injected into a person, often must be given several times to stimulate an immune response. Even then antibody production may decline after a time, leaving the individual vulnerable to the disease again. Booster shots may be required at regular intervals to raise immunity to protective levels. For instance, the diphtheria and tetanus immunizations are given initially at two-month intervals for a total of three doses. Immunity begins to decline after a few months, and booster shots are then administered periodically.
Why good? they immunize people against disease!!!!! why could they be bad? Adverse reactions, or side effects, have been reported for all existing vaccines. These reactions may range from a sore arm at the injection site to mild fever, joint pains, rash, or nausea, normally lasting only a short time. In some cases, however, severe reactions may occur.Oral polio vaccines, in which live virus is used, have been known to cause mild to crippling paralysis in some people who received the vaccines. However, the incidence of serious problems is rare approximately one case of paralytic polio per 9 million doses of vaccine. Vaccines are still among the safest and most beneficial preventive drugs available.
Gas Exchange ----------
Alveoli- they are very small so that the respiratory surface is much larger and much more gas can be exchanged, they are surrounded by capillaries so that cases are exchanged by diffusion as a consequence of the different partial pressures of oxygen and carbon dioxide, the barrier between the air in an albeolus and the blood in its capillaries is only about .5 micrometer; also, the alveoli have their own capillaries so that they can carry away the oxygen and CO2.
ventilation lungs- the exchange of air with the atmosphere takes place by bulk flow as a result of chagnes in lung volume.
Partial pressure- the total pressure (concentration) of a mixture of gases, such as air, is the sum of the pressures of the separate gases in the mexture. Oxygen makes up 21% of the gas in the air, thus 21 percent of the total air pressure results from the pressure of oxygen in the air. This is known as the partial pressure of oxygen.
Breathing- inspiration. This is only taking in air into the body; respiration is the breakdown of glucose using oxygen. Also, breathing is carried out by the body; respiration is carried out by individual cells.
Exercise- improves the functioning of the heart an dlungs- it increases stroke volume of the heart and increases tidal volume of lungs, which leads to a lowering of rate of both heart beat and ventilation rate- this is because exercise makes your heart and lungs stronger. When the heart is stonger, it can pump a larger volume of blood than before, and thus, the blood rate slows down. For the lungs, when it is stronger, it can inhale and exhale a larger volume of air and thus the breathing rate slows down. When you exercise, the amount of CO2 in the blood increases, which lowers the pH of the blood. This is detected by chemosensors in the aorta and carotid arteries, which send messages to the breathing center of the brain. Thbis then sends nerve impulses to the diaphragm and intercostal muscles to increase contraction/relaxation rates, which decreases the amount of CO2 in the blood. This is under involuntary control.
Health problem associated with gas exchange- The lung is normally protected by ciliated cells lining the trachea and bronchi. The cilia sweep out particles in the respired air that are caught in the mucus secreted by the goblet cells. These cilia are paralyzed by chemicals in cigarette smoke. Cancer cells arising in the bronchi generally do not have cilia.
Oxygen dissociation curves of adult and fetal hemoglogin (743) and myoglobin (745)- the amount of oxygen carried by the hemoglobin is related to oxygen pressure. The fetus must take up all its oxygen from the maternal blood. The hemoglobin of mammalian fetuses has a greater affinity for oxygen than does the hemoglobin of adult mammals, and so the oxygen tends to diffuse from the maternal blood to the fetal blood. Myoglobin is a respiratory pigment found in skeletal muscle. it is like hemoglobin but it has a greater affinity for oxygen. When the muscle is at rest or engaged in only moderate activity, the myoglobin holds on to its oxygen. It provides an additional reserve of oxygen for active muscle.
Method that CO2 is carried by blood- carbon dioxide is more soluble than oxygen in the blood, and a small amount of it is simply dissolved in the plasma. Most of the carbon dioxide is carried as bicarbonate ion (HCO3-). First carbon dioxide combines with water to form carbonic acid. This is catalyzed by the enzyme carbonic anhydrase found in red blood cells. Then carbonic acid, a weak acid, dissociates to yield bicarbonate and hydrogen ions. The direction this reaction takes depends on the partial pressure of carbon dioxide.
Bohr shift-??
Breathing- Air flows into the lungs when the air pressure is lower inside the alveoli than outside. It flows out when the air pressure is lower outside the alveoli. The pressure in the lungs is varied by changes in the volume of the thracic cavity. These changes are brought about by the contraction and relxation of the muscular diphragm and of the intercostal muscles. We inhale by contracting the dome-shaped diaphragm, which flattens it and lengthens the throacic cavity, and by contracting those intercostal muscles that pull the rib cage up and out.
Asthma- The lungs are especially vulnerable to allergic diseases such as asthma When the smooth muscle of the bronchial tree comes into contact with foreign particles such as pollen or certain environmental pollutants, it releases histamine, which causes the muscle to contract, restricting the bronchial airways.
Mouth to mouth resuscitation- 1. With the victim's head in the uptilted position, pinch the nostrils closed, take a deep breath, and place your mouth tightly over his mouth (do it through a handkerchief or thin cloth if you feel squeamish). Then blow quickly and deeply four times. After each time, raise your mouth and let air escape from the victim's mouth. Mouth-to-nose respiration may be used if the mouth cannot be opened or is badly injured. With small children, place your mouth over the mouth and nose. 2. If you feel resistance to your breath, and the victim's chest does not rise as you exhale or fall when you pause, the airway may still be obstructed. Bend the neck back farther and lift the chin higher. (Do not bend an infant's neck too far back or the airway will close.) If no obstruction is found, roll the victim on his side toward you and deliver four firm slaps between the shoulder blades. Then place the victim on his back again, put your fist just above the navel, and forcefully but carefully push once. These movements combined may force air out of the lungs and dislodge any foreign body trapped deeper in the airway. 3. After assuring an open airway, check for a pulse by placing your thumb and middle finger on the neck on either side of the windpipe. If there is a pulse, resume the inhalations and exhalations at the rate of one cycle every five seconds, or 12 a minute (practice the pace in advance with the second hand of a clock; it should feel quite normal). Use shallower breaths for children, about 20 a minute. For infants blow quick puffs of air from your cheeks. Mouth-to-mouth resuscitation must not be stopped for more than 15 seconds in adults, proportionately less in children, until the victim is breathing on his own. Keep checking the victim's pulse and watching for chest movement.
High altitudes- at extremely high altitudes there is a lower partial pressure of oxygen than at low altitudes. At high altitudes, survival depends largely on hyperventilation-extremely deep breathing. People that live at high altitudes have strong lungs. They have a larger vital capacity and a greater lung surface. For those who need to become acclimatised to high altitudes, red blood cell production increases and ventilation rate increases.
Homeostasis ----------
Homeostasis- refers to the ability of an organism to maintain a constant internal environment within a range that optimizes metabolic activities. It involves maintaining internal environment at a constant level or between narrow limits, including blood pH, water potential, oxygen and carbon dioxide concentrations, blood glucose and body temperature. It involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms.
Body temperature and thermoregulation- the constancy of temperature in homeotherms is mainained by an automatic system-a thermostat- in the hypothalamus. The thermostat receives and integrates information from widely scattered temperature receptors, compares it to the set point of the thermostat, and on the basis of this comparison, initiates appropriate responses. The skin receptors for hot and cold are probably the most important sources of information about temperature change. The hypothalamus itself contains receptor cells that monitor the temperature of the blood flowing through it. The hypothalamus acts on the anterior pituitary gland which releases a number of hormones involved in temperature regulation. It releases tropic hormones-which act on other endocrine glands to regulate their secretions, such as TSH, thyroid-stimulating hormone, and TRh, thyroid-reducing hormone,. The thyroid gland releases thyroxine which also plays a role in temp. regulation.
As the body temperature of a mammal rises above its thermostat setting, the blood vessels near the skin surface are dilated, and the supply of blood to the skin increases(vasodilation). If the air is cooler than the body surface, heat can be transferred from the skin directly to the air. Heat can also be lost from the surface by the evaportation of the saliva or perspiration. When the temperature of the circulating blood begins to fall below the thermostat setting, blood vessels near the skin suface are constricted (vasoconstriction) limitingheat loss from the skin. Metabolic processes increase. Part of this increase is due to increased muscular activity, either voluntary or involuntary, like shivering. Part is due to direct stimulation of metabolism by the endocrine (consists of glands which release hormones that are transported in the blood) and nervous sytems. Adrenaline stimulate s the release and oxidation of glucose. Thyroxine has a direct effect on the mitochondria. Nerves to fat increease its metabolic breakdown. The hair on the layer of skin are pulled upright by erector muscles in the skin in order to trap air which insulates the surface of the skin.
Levels of blood glucose-Glucose and other monosaccharides are absorbed into the blood from the intestinal tract and are passed directly to the liver by way of the hepatic portal vein. The liver converts some of these monosaccharides to glycogen and fat, storing enough glycogen to satisfy the body's needs for about four hours. The fat is stored in fat cells, which can also form fat from glucose. Similarly, the liver breaks down excess amino acids (which are not stored) and convets them to glucose. The nitrogen from the amino acids is excreted in the form of urea, and the glucose is stored as glycogen. Whether the liver takes up or releases glucose and the amount it takes up or releases are determined primarily by the concentration of glucose in the blood. The concentration of glucose is, in turn, regulated by a number of hormones and is influenced by the autonomic nerbous system. The hormones involved include insulin, glucagon, and somatostatin, all formed in the pancreas. pancreas-The pancreas is composed of two types of tissue: the islets of Langerhans, which are named after the 19th-century German pathologist Paul Langerhans, and acinar cells. The islets of Langerhans, made up of alpha and beta cells, are patches of tissue scattered among clusters of acinar cells. Alpha cells in the islets produce glucagon, a hormone that raises blood sugar levels by converting stored carbohydrates into the sugar glucagon, which is the primary fuel of cells. Beta cells secrete insulin, a hormone that allows cells to remove glucose from the bloodstream and to use it. Glucagon and insulin work together to control the amount of sugar stored in the body. Insulin stimulates the uptake of glucose by cells, thus decreasing blood glucose. Glocagon promotes the breakdown of glycogen, thus increasing blood glucose. Somatostatin has a variety of inhibitory effects that collectively help to regulate the rate at which glucose and other nutrients are abosorbed from the digestive tract.
Negative feedback- ie. a house thermostat- when the temperature in your house drops below the preset thermostat level, the thermostat turns the furnace on. When the termperature rises above the preset temperature the thermostat turns the heat off. A deviation from a 'preset' condition stimulates a response that reduces the deviation.
water potential- water molecules move from one place to another because of differences in potential energy. water moves from a region where water potential is greater to a region where water potential is lower. A good example is water running downhill in respone to gravity.
Reproduction ----------
Sexual reproduction- a type of reproduction which involves two individuals; half the genes of one individual are donated to the offspring, and half the genes of the other individual are donated to the offspring. This promotes variability.
Spermatogenesis- The sperm are produced within the seminiferous tubulules. They contain two kinds of cells: the Sertoli cells and the spermatogenic (sperm-producing) cells. The spermatogenic cells pss through several stages of differentiation. cells in the first stage of spermatogenesis, the spermatogonia, line the basement membrane of each seminiferous tubule. They are diploid. They dicide continuously. SOme of the cells produced by these mitotic divisions remain undifferentiated, wheras others, in the course of their successive mitotic divisions, move away from the basement membrane and begin to differntiate, giving rise to primary spermatocytes. They undergo the first meiotic division to produce two secondary spermatocytes. They have 23 chromosomes each. These undergo the second meiotic division to poduce spermatids, each of which contains the haploid number of chromosomes. These develop into spermatozoa. Spermatid differentiationˆ within the golgi complex, vesicles containing small, dark granulesˆacrosome. contains enzymes to penetrate egg. acrosome formationˆ centrioles move to cell membrane which initiate the assembly of tubulim dimers to microtubules to make a flagellum for sperm. It has a 9+2 structure characteristic of eukaryotic cilia and glagella. Mitochondria aggregate about its basal end, makeinga continuous spiral for energy. Nucleus condenses.
Oogenesis- primary oocyteˆ prophase of first meiotic divisionˆ females mature sexuallyˆ meiosis 1 resumesˆ 1 polar body and 1 secondary oocyteˆfertilizationˆ second meiotic divisionˆ ovum and polar body. (primary oocyte-as the nucleus divides, the cytoplasm of the oocyte bulges out. one set of chromosomes moves into the bulge. The rest of cellular material is the large secondary oocyte. Polar body is much smaller.)
Oogenesis and spermatogenesis compared- there are a lot less oocytes than sperm cells. 300-400 million sperm in a single ejaculation of average male. 2 million primary oocytes only. Takes a helluva lot longer to make egg cell vs. sperm. Egg- birth to fertilization untill it has completed meiosis 2. Gametes in female are released monthly, with males when they are excited.
Hormones involved ----------
males- The testes are the major source of male hormones, known collectively as androgens. The principal androgen, testosterone, is necessary for the formation of sperm cells. It is a steroid, produced primarily by the interstitial cells of the testes. Other androgens are produced in the adrenal cortex. In puberty testosterone is responsible for the enlargement of the penis and testes and also of the prostate and other accessory organs. The production of testosterone is regulated by a negative feedback system involving luteinizing hormone, LH. It is produced by the pituitary gland under the influence of the hypothalamus. FSH acts on the Sertoli cells of the testes and through them on the developing sperm. Regulation of FSH- a protein molecule secreted by Sertoli cells. It inhibits FSH production.
Females- controlled by the hypothalamus. The hormones involved are progesterone, estrogen(the female sex hormones), and the gonadotropic hormones LH and FSH, and the gonadotropin-releasing hormone GnRH from the hypothalamus. At the beginning of the menstrual cycle, hormone levels are low. After a few days, FSH and LH are released and this stimulates the growth of a follicle in the ovary. As the follicle enlarges, it secretes increased amounts of estrogens, which stimulate the regrowth of the endometrium in prparation for implantation of a fertilized egg cell. The rapid rise of estrogen triggers an increase in the release of LH by the pituitary. The spurt of high LH stimulates the follicle to release the oocyte, which begins its passage to the uterus. Under the stimulus of LH the follicle turns into the corpus luteum. They secrete progesterone as well as estrogens. As progesterone levels increase, estrogens and progesterone inhibit the production of GnRH and so of the gonadotropic hromones LH and FSH from the pituitary. If pregnancy does not occur, the corpus luteum is reabsorbed and the production of ovarian hormones drops. Without hormonal support, the endometrium canno longer sustain itself and a portion of it is sloughed off in the menstrual fluid. In response to low levels of ovarian hormones, the lebel of pituitary gonadotropic hormones begins to rise again· etc.
Secondary sexual characteristics ----------
Males- Testosterone also has an effect on the growth of the larynx, accompanying a deeper vboice, an increase in skeletal size, and a distribution of body hair. They also stimulate muscle tissue. These latter ones are called secondary sex characteristics. Females-changes in the distribution of body fat, growth of body hair and underarm and pubic hair. Also the girls hips widen and breasts grow due to the growt of mammary glands. Also growth spurt.
Semen- spermatozoa move out of the epididymis where sperm are stored, into the vas deferens, to the seminal vesicle. The seminal vesicles secrete a fructose-rich fluid that nourishes the sperm cell. This fluid contains a high concentration of prostaglandins, which stimulate contractions in the musculature of the uterus and oviducts to assist the sperm. The prostate gland adds a thin, milky, alkaline fluid that helps neutralize the normally acidic pH of the female reproductive tract. These secretions all make up semen.
Fertilisation- the fusion of an egg cell and a sperm. Copulation is sexual intercourse. Fertilisation must occur in an oviduct because if the cell has traveled any further it will be dead. The egg cell has a protective layer around it called the vitelline envelope. A sperm uses the enzymes in its acrosome to get into the cell and through the protective layer. Once a sperm cell has entered the egg cell, the egg cell changes its structure so that no single sperm can enter it. The nuclei of the two cells fuse. fertilisation results in 1) changes in the outer surface of the egg that prevent entry of other sperm cells 2) metabolic activation of the egg 3) introduction of the genetic material of the fater 4) cleavage.
Embryo Development- At about 36 hours after fertilization, the fertilized egg divides to form two cells, at 60 hours, the two cells divide to form four cells. At three days, the four cells divide to form eight. This ball of cells is called a blastocyst. By about 5 days after fert. it consists of some 120 cells. 6 days after fert. the ball reaches the uturus and penetrates the endometrial tissues-called implantation. It becomes surrounded by ruptured blood vessels and the nutreint-filled blood escaping from them.
Human chorionic gonadotrophin (HCG)- after implantation, the developing placenta makes HCG some of which is lost in the urine. This hormone serves to keep the corpus luteum secreting progesterone and estrogen so that the placenta will continue to be maintained. A monoclonal antibody to HCG is produced commercially. Although several commercial tests exist, many consist of dye molecules atached to monoclonal antibody in a plastic holder. When this is dipped into urine which has HCG the complex of hormone/monoclonal antibody/dye moves to appear as a coloured line.
Placenta-By the end of the thrid week after conception, the placenta covers 20 percent of the uterus. It is a disc-shaped mass of spongy tissue through which all exchanges between mother and embryo take place. It is formed as a result of the itneractions ofa maternal tissue, the enometrium, with the eextraembryonic chorion, and has a rich blood supply from both. Molecules, including food and oxygen diffuse from the maternal bloodstream through the placental tissue and into the blood vessles that carry them into the embryo. Similarly, carbon dioxide and other waste products from the embryo are picked up from the placenta by the maternal bloodsteam and carried away for disposal through the mother's lungs and kidneys. By the end of the third month of pregnancy, the placenta has completely replaced the corpus luteum as a source of estrogens and progesterone. Chroionic gonadrotropin is no longer produced by the chorion and the corpus luteum degenerates. fetus-supported and protected by the amniotic sac and amniotic fluid. The fetus obtains its nutrients by exchanging materials between its blood and maternal blood in the placenta- through its umbillical chord.
Birth-divided into three stages, labour, delivery and afterbirth. Labor is dicided into three sates: dilation, expulsion and placental stages. Dilation begins with the onset of contractions of the uterus. It ends with the full dilation, or opening, of the servix. At the beginning, uterine contractioons occur at intervals of about 15 to 20 minutes and are relativley mild. Expulsion bigins with the full dilation of the cervix and the appearance of the head in the cervix called crowning. The thrid, or placental stage begins immediately after the baby is born. It involves contractions of the uterus and the expelling of fluid, blood and finally the placenta with the umbilical cord attached, also called the afterbirth.
Family planning and contraception ----------
Vasectomy-the vas deferens on each side is severed, and the cut ends are folded back and tied off, preventing the release of sperm from the testis. This is 100% effective. Tubal ligation-the oviduct is severed and tied. This prevents the passage of oocyte to uterus. Also 100% effective. The pill-inhibits secretion of FSH and LH thereby preventing follicle maturation and ovulation. 100-90 % effective. Contains progesterones and estrogens Condom-covers the male penis and prevents sperm from entering the vagina. 97-64% effective, depending on the quality.
Amniocentesis and chorionic villus sampling- amniocentesis- fluid samples are taken from the amniotic cavity. They contain cells that have been sloughed off by the embryo. It cannot be performed until the sixteenth week of pregnancy. It can be used to diagnose nearly 400 conditions from chromosmal abnormalities to biochemical disorders CVS- a small sample of tissue is remobed from the chorion, which is identical to the empbryo itself. It is taken via the vagina.
In vitro fertilization (IVF), the process of uniting two human germ cells (sperm and egg) outside the human body and in an artificial environment; term often includes the process of embryo transfer; first successful human birth using this technique took place in England 1978; the process itself and related techniques such as the freezing of eggs, sperm, or embryos for future implantation have raised ethical questions, including the fear of experimentation with human fetuses.
Excretion ----------
Excretion- the removal of waste substances from the body. Blood can only function as an efficient supply and sanitation medium only because cellular wasters are constantly removed from it. Excretory products in plants include oxygen, and in animals include carbon dioxide and nitrogenous compounds.
Differences in excretion- Surplus amino acids must be degraded to relatively harmless nitrogen containing compounds. Freshwater fish and amphibian larvae can get rid of ammonia although higly toxix because it can be diluted by the readily available water. Marine species need to conserve water because the environment is hypertonic compared to their own interstitial fluid. They convert nitrogenous wastes to the less toxic and less soluble urea and trimethylamine oxide. likewise adult amphibians need to conserve water so they can also poduce urea. Birds are unable to carry too much water so they excrete uric acid which is insoluble and expelled as a paste. Insects and reptiles also excrete uric acid, an end product of purine metabolism. Mammals excrete the urea produced in the ornithine cycle. Some mammals produce very concentrated urine because they have a long loop of henle.
Osmoregulation- regulation of water balance in the body.
Ultrafiltration- The blood enters the kidney via the renal artery, which divides into arerioles and eventually into the afferent arteriole which leads into the glomerulus. The afferent arteriole and the efferent arteriole, which leads out of the nephron, the unit of function in the kidney, are constricted to keep the blood pressure within the glomerulus at about twice that of the pressure in other capillaries. The renal arteries branch out directly from the aorta, which also keeps the blood enetering the kidneys at relatively high pressure. This is important because this pressure difference causes about one fifth of the blood plasma to force through the walls of the glomerulus into the bowman's capsule. This process is called pressure filtration. From the bowman's capsule the plasma which is forced out of the glomerulus goes into the lumen of the renal tubule. The plasma that was forced out is now called the filtrate. Reabsorption- The water and solutes which entered the tubule during filtration are returned to the bloodstream. These molecules are those which we need in the body. They are reabsorbed through the walls of the tubule into the blood of the surrounding capillaries. This reabsorption is highly selective. Water, sodium, chloride ions, most of the bicarbonate, and all of the glucose are reabsorbed back into the bloodstream. Urea and ammonia and some water remain in the tubule. The glucose in the filtrate is actively reabsorbed in the prosimal convoluted tubule. The active transport of glucose is done by the epitelial cells of the tubule. They contain a large number of mitochondria in order to produce most of the energy in the form of ATP which is needed for active transport. Sodium, potassium, phosphate, and hydrogencarbonate ions are also actively transported from the proximal convoluted tubule. During the later stage, through Henle's loop and the distal convoluted tubule, most of the remaining filtrate is further selectively reabsorbed.
Formation of hypertonic urine- The regulation of water in the kidney is a complex process which allows organisms to consverve water. This is due for one by the fact that certain regions of the tubule are less permeable than others. The rate of water movement depends on the permeability of the tubule and so the differrence of permeability throughout the tubule means different rates of water movement throughout the tubule. The ascending limb of the loop of Henle, the distal convoluted tubule and the collecting duct have a restricted permeability of water while the proximal convoluted tubule and the descending limb of the loop of Henle are freely permeable to water. Most water is reabsorbed out of the tubule in the region of the proximal convoluted tubule. This occurs because liquid and small solutes are lost from the blood as they pass into the tubule and this increases the concentration of the blood. This allows the blood to reabsorb the water by osmosis. The active pumping of sodium ions across the proximal tubule increases the concentration in the tissue surrounding the tubule. This allows the tissues to reabsorb the water by osmosis. The most important part of the reabsorption of water takes place due to a mechanism called the countercurrent multiplier. The way in which it works is due to the different permeability of the loop of Henle. As the fluid goes up into the ascending limb of the loop of Henle, sodium and chloride are pumped out of the tubule due to the lower concentration of these ions in the surrounding tissue. As the ions pass into the tissue, the tissue becomes more concentrated, and so it would be expected that the water in the ascending limp of the loop of Henle would follow the ions, but due to the low permeability of water and the easy permeability of sodium and chloride ions the water remains in the tubule. The descending limb of the loop of Henle is easily permeable to water but less permeable to sodium and chloride. The tissue surrounding both limbs of the loop now contain sodium and chloride ions. Water from the descending limb leaves the tubule due to the difference of concentration in the tissues. The fluid in the tubule becomes more concentrated. As it comes up the ascending limb, however, sodium and chloride ions are pumped into the surrounding tissue again. The point of this is only to produce a very high concentration at the very tip of the loop. This produces a strong concentration gradient across the kidney. The fluid flows through the distal convoluted tubes and into the collecting duct. The tissue surrounding the collecting duct is more concentrated as the duct goes further down. This leads to water diffusing out of the duct and into the surrounding tissue due to the concentration gradient. This makes the urine very concentrated. ADH-antidiuretic hormone- is formed in the hypothalamus, a major regulatory center in the brain. It acts on the membranes of the collecting ducts of the nephrons and increases their permeability to water, and so more water moves, by diffusion back into the blood.
Kidney dialysis machine- renal dialysis by kidney machine depends only on passive diffusion. The blood of the patient, taken from a vein, passes through tubes or between membranes of partially permeable materials. An enormous surface area is required and the process takes 4-6 hours repeated three times a week. A dialysis fluid on the other side has the same water potential, and similar solute concentrations, to the blood plasma except that there is no urea. Urea therefore diffuses from the blood and is washed away with the dialysis fluid. There should be no other net change, but if necessary water and other solutes can be replenished before the dialysed blood is returned to the patient.
The liver ----------
Circulation of blood to the liver- The liver circulation is a portal system, in the liver's case a hepatic portal system. Venous blood collected from the capillaries of the digestive tract is shunted via the hepatic portal vein through the liver. There it goes through a second capillary network before it is amptied into the inferior vena cava. In this way, the products of digestion can be directly processed by the liver. THe liver also receives freshly oxygeneated blood directly from a jajor artery, the hepatic artery.
Storage of nutrients- It stores and releases carbohydrates, it processes amino acids, converting them to carboyhydrates, channeling them to other tissues of the body, and synthesizing essential proteins such as enzymes and clotting factors from them. it manufactures the plasma proteins that make the blood hupertonic in relation to the interstitial fluids and so prevents the osmotic movement of water from the loodstream to tissues. It is also the major source of the plasma lipoprotein including LDLs and HDLs that transport cholersterol, fast, and other water-insoluble substances in the bloodstream and is of centraol importance in the regulation of blood cholesterol. It stores fat-soluble vitamins such as A D and E. It produces bile. (contains HCO3-, bile salts and bile pigments.) Bile is stored in the gallbladder and delivered to the gallbladder and small intestine through the bile duct) The liver inactivates a number of hormones, thus playing an important role in hormone regulation. it also breaks down a variety of foreign substances some os which, alcohol for instance may form metabolic products that damage liver cells and interfere with their functions.
Hemoglobin- The liver breaks down hemoglobin from damaged and dead red blood cells to bilirubin, a yellow pigment; it is released into the bile and excreted through the intestinal tract. AAfter about 4 months, Kupffer cells in the liver destroy the red blood cells. The iron is stored and the protein broken down to amino acids.
Topic 9: Cell Respiration and Photosynthesis
Cell respiration ----------
Oxidation-the loss of an electron. Frequently involves gaining oxygen or losing hydrogen. Reduction- gain of an electron or hydrogen or loss of oxygen.
Glycolysis- The splitting of glucose. A 6-carbon sugar is converted into two trhee-carbhon atom compounds called pyruvic acid, with a net gain of two ATP and two NADH + H+. It requires two ATP molecules and results in four, hence the net gain is two ATP molecules. Phosphorylation-addition of a phosphate group to a molecule. It is a process in which ATP is made in vivo.
Mechanics of glycolysis- 1) an energy input is required- a phosphate group from ATP is attached onto the glucose molecule ˆ glucose 6-phosphate. 2) 6-carbon sugarˆ 5-carbon sugar called fructose. (fructose 6-phosphate) 3) fructose gets another phosphate from ATP ˆ fructose 1,6 (with phosphate groups on the 1 and 6 carbon) 4) fructose ˆ two 3-carbon molecules, dihydroxyacetone phosphate and glyceraldehyde phosphate. 5)oxidation of glyceraldehyde molecules (hydrogen atoms with electros are removed- and NAD+ is reduced to NADH and H+) 6) a phosphate is pulled off and put on an ADP molecule to make ATP. 7) a bunch of other stuff happens, but basically you end up with two molecules of pyruvic acid, a 3-carbon sugar.
Aerobic respiration- this takes place in the mitochondria. They are surrounded by two membranes- the outer one is smooth, and the inner one folds inward. These folds are called cristae. Within the inner compartment of the mitochondrion, surrounding the cristae, is a dense solution known as the matrix. It contains a bunch of molecules involved in respiration (like enzymes, coenzymes, water phosphates etc.)
Alllrighty then: respiration. 1) First step is the oxydation of pyruvic acid. It turns into Acetyl CoA. Which is a two carbon sugar. (CH3CO). and also: the hydrogen of the carboxyl group reduces a molecule of NAD+ to NADH. (acetyl plus coenzyme a: acetyl CoA). 2) The acetyl CoA goes into the kreb's cycle·. 3) Acetyl CoA+ a four-carbon compoundˆ 2 + 4 = 6-carbon compound, get it?? 4) C6 (citric acid)ˆ C5 (alpha-ketoglutaric acid)ˆ C4 (succinic acid)ˆC4 (malic acid)ˆC4 (oxaloacetic acid)ˆend 5) Some of the potential energy of the glucose molecule has been used to produce AATP from ADP. Most of the energy, howeber, remains in electrons removed from the C-C and C-H bonds and passed to the electron carriers NAD+ and FAD. These electrons are still at a high energy level. 6) Final stage: these high energy level electrons are passed step-by-step to the low energy level of oxygen. The energy they yield in the course of this passage is ultimately used to regenerate ATP from ADP. This step-by-step pasasge is mad epossible by a series of electron carriers, each of which holds the electrons at a slightly lower level. 7) These carriers=electron transport chain. Muy importanto. Among the principal components of the electron transport chain are molecules known as cytochromes. The iron atom of each cytochrome alternately accepts and releases an electron, passing it along to the next cytochrome at a slightly lower energy level until the electrons, their energy spent, are accepted by oxygen. The energy released in this downhill passage of electrons is harnessed as we shall see to form ATP molecules from ADP. Such ATP formation is known as oxidative phosphorylation.
Oxidative phosphorylation- the way in which ATP is formed from ADP and phosphate as electrons pass down the electron transport chain. The process is powered by a gradient of proton