Topic 1 - Cells

From KstructIB

I, Sen, do state that, to the best of my knowledge, the following material is not copyrighted. I also state that someone who can spell should look at this document for my errors! Also, my html skills suck, if there is a more efficent method, I would be greatful to know.

1.1 Cell Theory

Robert Hooke(1665): Published first book on cells. Discovered cells when looking at cork under a microscope. Discovered cell structure of plants.

Anton von Leewenhoek (1650-1700):Dutch. First observed protists. With a simple lens(x200), he observed unicellular organisms & nuclei. By using his ability to grind lenses, he greatly improved the microscope as a scientific tool. He discovered bacteria, protozoa and other small life-forms which he called 'tiny animals'.

Mattias Schleiden(1838): Deduced theory of 'photogenesis' which states that all living things are made of cels or their derivitives.

Theodore Schwann(1839): With Schleiden, Schwann deduced the cell theory- that all animals and plants are made of cells and that within an organism all the cells are identical. Discovered Schwann cells.

Rudolph Virchow (1855): Deduced that all cells are created by other cells. Demonstrated that cell theory applies to diseased tissue as well as living tissue.

Jansen: Invented compound microscope.

Light Microscopes: Light from a source beneath the stage is transmitted through the two lenses in a series, the objective and the ocular (eyepiece) lenses to provide magnifications. Cannot resolve details better than about 0.2 mm(micrometers)

Advantages of light microscopes:

• Enables user to see larger structures within eukaryotes and distinguish individual prokyrotes.
• They are user-friendly: small, portable, easily-prepared slides, relitivly cheap to buy and maintian.
• Both living and dead material may be viewed.
• Material is rarely distorted by preperation.
• Thicker materials may be viewed
• Allows experimenter to view image directly.
• Allows for specimen to be observed in natural state.
• Slides are simple to prepare
• Faster
• Color
• Can observe movement.

Electron microscopes: Uses an electron beam instead of a light beam, and electromagnets instead of lenses. Electrons are recorded on a photographic plate, which forms an image on screen.

Advantages or electron microscopes:

• Magnifies over 500,000x
• Resolving power for biological specimin around 1nm
• 3-D view instead of one.
• Interior view
• See organelles than cannot be observed w/ light microscope.

'Resolution': Ability to percieve fine detail. Expressed as the minimmum distance between two points for them to be visually distinct. Depends on the lens quality and the wavelength of light used.

'Magnification: The ratio between the size represented on the microscope and the actual size.

Organelle: A small body inside a cell with a specilised structure that performs a specific function. It also has its own protective membrane.

Relitive Sizes:

• 1nm: Membrane Thickness
• 10nm: Viruses
• 100nm: Bacteria
• 1-10mm(read'micrometer'): Organelles
• less than or equal to 100mm(micrometers): Cells

OR:

• 1 nm: Molecules
• 10 nm: Cell Membrane
• 75 nm: Virus
• 100 nm: Macromolecules
• 1 mm(micrometer): Bacteria
• 3 mm: Organelles
• 10 mm: Cell

Surface area to volume ratio: *The rate of the metabolism of a cell is a function of its mass to volume ratio.* The more active a cell's metabolism, the more material must be exchanged if the cell is to continue to function. The smaller the cell, the more efficent it is. Larger cells require more energy, but their surface area to volume is closer to one, making them less efficent.

Cell Nucleus: A membrane enclosed organelle containing genetic information.

Possible outdated information:

• All living things are made from cells, and all cells are created by other cells.
• A virus is a non-cellular structure of DNA or RNA surrounded by a protein coat.
• Unicellular organisms carry out all the functions of life
• In multicellular organisms, all cells contain genes. By only expressing some of their genes, the cells in multicellular organisms differntiate to carry out specialized jobs.
• A tissue is an integrated group oi cells that have a common structure and function.
• An organ is a center of the body composed of several different types of tissue and carries out a bodily function.
• An organ system is a group of organs the specialize in a certian function together.

1.2 Prokaryotic Cell Structure

Prokaryote: (pro before + karyon kernel) A cell that lacks any membrane bound organelles. Prokaryotes also belong to their own kingdom, bacteria and blue-green algee.

Ribosomes: Small cytoplasmic granules found in all cells. They are smaller than the ribosomes found in eukaryotic cells. They occur singly or in groups called polysomes. They are made of RNA and protein. They are important in protein synthesis. Produces protein for use inside cells.

Mesosomes: Resembles the mitocondria in eukaryotes. They are infoldings of the cell membrane and are important in/site of resperation. Primitive vacoules(deep furrows) to store food or waste.

Slime-Capsule: Surrounds the cell wall of bacteria, it helps to keep the cell from being digested or drying out. Keeps away predatory protazoam white blood cells and bacteriophages.

Flagellum: A small projection from a cell wall that propells a cell. It is an organelle. Flagullum are accanged around the cell in nine doublets with two single microtubules in the middle. This arrangement is known as the "9+2" pattern.

Cell Wall: Gives the cell it's shape, protects the cell and prevents the cell from obsorbing too much water.

Cell Surface Membrane:Controls the movement of things in and out of the cell. Protects the organellesinside from the outside enviornment. It is made of phospholipids.

Plasmid: An extra-chromosomal, independantly replicating, small, circular DNA molecule. Enables production of antibiotics or resistance to anti-biotics.

Naked Nucleic Acid: Contains the hereditary information of the cell. It regulates protein production.

Cytoplasm: A gelatonus, semi-trasparent fluid that fills most cells.

Cytoskeleton: A structure that maintains the shape of the cell, protects the cell and enables motion, The cytoskeleton plays an important role in inter-cellular transport and cellular division.

Possible Outdated Information:

• Prokaryotes show a wide range of metabolic activity including fermentation, photosynthesis and nitrogen fixation. Eukaryotic Cell: contains organelles (discrete structures within a cell that carry out specific functions) Contains: 80s ribosomes: used for protein synthesis Rough Endoplasmic Reticulum: stores proteins and has ribosomes (rough) Smooth Endoplasmic reticulum: stores proteins, but does not have ribosomes (smooth) Lysosomes: containing digestive enzymes Golgi Apparatus: modifies and 'repacks' proteins Mitochondrion: (similar to mesosomes in prokaryotes)are the site of aerobic repiration Nucleus: an organelle that stores linear DNA Nucleolus: stores RNA within the nucleus Centrioles: vital for reproduction (production of spindle fibres) Chloroplast(in plants):organelles Vacuole: stores excess liquids Cytoskleteon: little fibres to help rigility