Biological Molecules

1. Bonding
   1. Hydrogen Bonding

      Annotations:

      • Weak electrical attraction between the d+ve hydrogen and the d-ve oxygen on the next molecule. 
2. Properties
   1. Ice
      1. Less Dense than water

         Annotations:

         • Because hydrogen bonds hold water in a rigid lattice.
   2. High Specific Heat Capacity
      1. Body temp

         Annotations:

         • A lot of energy needed to increase the temperature of water. 
         • We are largely water so large changes of water in the external environment have relatively small effects on your body temp. (as with all living organisms)
   3. High Boiling Point

      Annotations:

      • Due to hydrogen bonding
      1. Sweat

         Annotations:

         • Humans use this property, when liquid sweat lies on the surface of the skin, sweat absorbs the heat energy from the body as it evaporates. The heat need is called latent heat of evaporation. It is our major cooling mechanism
         • Same as plant leaves in hot climate cool down by the evaporation of water on their surface. 
   4. Solvent
      1. Dissolving
         1. Metabolic reactions

            Annotations:

            • Many reactions will only take place in a solution as it is easy for the ions/molecules to react with other ions/molecules
            • water can flow so it can carry dissolved substances (eg glucose) from one place to another. This happens in our blood, xylem and phloem and urine. 
   5. Viscocity and Density

      Annotations:

      • most living organisms, containing a lot of water, have a density which is quite close to that of water. This makes it easy for them to swim as they can slightly change their density by filling or emptying air from parts of their body, to float or sink.
      1. 1.0 gdm-3
   6. Cohesion and Surface Tension

      Annotations:

      • Surface tension: On the surface their is only cohesion from molecules below so they are pulled downwards. These pulling forces draw them closer together than other parts of the pond so it is a strong layer.

1. Structure
   1. Amino Acid
      1. Peptide bond
         1. Hydrolysis

            Annotations:

            • Where water is used to break down a substance. E.g. poypeptide + water --> amino acids
         2. Condensation

            Annotations:

            •  a condensation reaction where water is also produced. 
      2. Polypeptide

         Annotations:

         • Chain of amino acids with peptide bonds
      3. Amine-NH2 Acid-COOH
      4. R Groups
   2. Primary structure

      Annotations:

      • The sequence of amino acids
      • 20 different amino acids found naturally
      1. Secondary structure
         1. Tertiary
            1. Quaternary

Annotations:

• General formula Cn(H2O)n

1. Monosaccharides
   1. Benedicts solution
      1. Add Benedicts soln.
         1. Heat
            1. Blue= no reducing sugar
            2. Green=some
            3. Brown= more
            4. Red=most
      2. Reducing sugars Cu2+ reduced to Cu+ as sugar gives electron.
   2. Glucose
      1. Alpha

         Annotations:

         • OH on carbon-1 is undA
         • glucose+glucose-->maltose-is only made of a glucose glucose+galactose-->lactose (animals) glucose+fructose-->sucrose (plants)
      2. Beta

         Annotations:

         • OH is aBove
   3. Properties
      1. Sweet
      2. Form crystals
      3. Soluble in water
2. Polysaccharides
   1. Starch
      1. Amylose
         1. Thousands of a glucose joined together in a chain
            1. Joined by a glycosidic 1,4 bonds
         2. Chains of molecules coil into a compact helix
      2. Amylopectin
         1. Thousands of a glucose joined together
            1. Joined by a 1,4 and 1,6 a-glycosidic bonds
               1. 1,6 bonds creates branches
      3. Structure
         1. Compact- good for storage
      4. Iodine test

         Annotations:

         • Add Iodine soln, if starch is present, soln turns blue. (original colour orange/brown)
   2. Glycogen
      1. Thousands of a glucose joined together in a chain
         1. Both 1,4 and 1,6 (unlike amylose)
      2. Branched chains (shorter than amylopectin)
      3. Structure
         1. Arranged around glycogenin (protein) giving it a globular arrangement
         2. Food store in animals
         3. Compact
         4. Unreactive
         5. Insoluble, forming granules in liver and muscle

            Annotations:

            • Important cos otherwise would affect conc. gradient as it would dissolve in water and affect osmosis.
   3. Cellulose
      1. Made of b glucose
         1. 1,4 glycosidic bonds
      2. H bonds link adjacent chains

         Annotations:

         • 60-70 chains form microfibrils, the number of h bonds give microfibrils TENSILE STRENGTH. 
         • Microfibrils held together by H-bonds form CELLULOSE FIBRES
      3. Layers of fibres running in dif. directions form CELL WALLS