Jen Parks - Topic 2

From KstructIB

Topic 2: The Chemistry of Life

Elements of Life

2.1.1 The three commonest elements of life are carbon, hydrogen, and oxygen.

2.1.2 A variety of other elements are needed by living organisms including nitrogen, sulfur, phosphorus, iron and potassium.

2.1.3 Nitrogen- It is a constituent of proteins, nucleic acids, and many other of life’s molecules. Sulfur- It appears in amino acids as a sulfhydral group. (A sulfur atom covalently bonded to a hydrogen atoms) Phosphorus- It can always been combined with oxygen to become a phosphate. It is very important in the making of ATP. Iron-? Potassium-?

2.1.4 An atom is the smallest indivisible unit of an element. Ion is positevely or negatively charged.

2.1.5 Organic- A molecule containing carbon and generally produced by living organisms.

2.1.6 Water molecules are polar, each with slightly positive and negative regions. For this reason, they tend to attrract each other, forming hydrogen bonds. Transparency- By being transparent, sunlight can reach greater depths and supply the water world with light energy. Cohesion- (Cohesion is the attraction between similar substances. Adhesion is the attraction between two dissimilar substances.) Acting together, Cohesion and Adhesion give water a special property known as capillarity. Basically this is when the height to which water rises is inversely proportional to the diameter of the tubing. Surface tension- Where air and waer meet, the water molecules at the interface have a much greater attraction to other water molecules then to the air above them. The surface thus forms a tough, elastic film of hydrogen-bonded water molecules. Temperature- Water’s high specific heat (resitance to temperature change) is attributed to the stability of humerous hydrogen bondfs. As water cools its density decreases, reaching a low-temperature minimun at 0o C. Solvent properties- The fact that water is capable of dissolving many organic and inorganic particles.

2.1.7 Plants, animals, and the many other forms of life use water, incorporating it for a time in their cells as they go about their chemical activities. Eventually, all this water is returned to the cycle of the atmosphere and oceans as the organisms respire or die. Think about it this way, after it has rained it is much cooler, or at least in the desert it is. It supplies water to desert plants that would optherwise dry up and die in the heat of the sun. As far as transport, fish swim in the water to move around. They have adapted to the water. Bugs glide along the surface of pools, etc. because of the surface tension.

2.2 Carbohydrates, Lipids and Proteins

2.2.1 The basic structure of an amino acid:

COOH 
     | 
R-C-H 
     | 
    NH2

2.2.2 The ring structure of α-D-glucose:

H 
 | 
H- C6-OH 
| 
      H    C5-----------O          H 
       \    /         \        / 
        >C4   H   HO    C1< 
      /      \  |              |    /       \ 
  HO   C3---------C2          OH 
   |       | 
  H              OH 

2.2.3 The basic structure of flycerol and a generalized fatty acid:

         H          H                       H 
          |           |           | 
H-----C-----------------C -----------------C-----H Glycerol 
          |           |           | 
         O          O                       O 
         H                       H                       H 
       + 
         H                       H          H 
         O                       O                        O 
          |                         |                          | 
         C=O                  C=O                   C=O 3 Fatty Acids 
          |          |           | 
     H-C-H     H-C-H      H-C-H 
          |          |           |          = 
     H-C-H     H-C-H      H-C-H 
                       |          |           | Triglyceride 
     H-C-H     H-C-H      H-C-H 
                       |          |           | 
     H-C-H     H-C-H      H-C-H 
          |          |           | 
         H                      H                         H 

2.2.4 In the synthesis of a triglyceride, dehydration linkages form between the three hydroxyl (-OH) groups of glycerol and the hydroxyl (-OH) groups of three fatty acids. The products are one molecule of triglyceride and three of water. Dehydration is also referred to as Condensation. Peptide bonds form through the dehydration process. They are linkages that join two amino acids by their carboxyl and amino groups. Hydrolysis is the reaction of a compound with water such that the compound with water such that the compound is split into two parts by the breaking of a covalent bond, and water is added in the place of the bond, an –OH group going to one subunit and an –H group going to the other.