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Chemical Elements are Joined Together to Form Biological Molecules 1.1 -…

- - - - Polar molecule; oxygen end - -ve charge, hydrogen atoms - +ve charge
      - Uneven distribution of charge - Dipole
      - When 2 water molecules are in close contact, opposing charges attract each other forming a hydrogen bond
      - Individually hydrogen bonds are weak, many form lattice-like framework which is much strronger
      - This attraction between water molecules - Cohesion
    - - Solvent - Ions + polar molecules can dissolve in water, non-polar molecules cannot
      - Transport Medium - Blood is largely water, transports many dissolved substances around body, minerals dissolved in water are transported from root to leaves via xylem in plants
      - Chemical Reactions - Transport allows chemical reactions to take place when particles or molecules meet
      - High Specific Heat Capacity - Large amount of heat needed to raise temp, Prevents large fluctuations, Keeps temp of aquatic environments stable so organisms don't have to endure extremes, Allows enzymes within cells to work effectively
      - High Latent Heat of Vaporisation - Due to cohesion, large amount of heat energy needed to change water to gas, process of evaporation is very effective way of cooling body, evaporation of water from surface causes cooling
      - Cohesion - Attraction between water molecules allows water to be transported, in long columns, up xylem vessels
      - Surface Tension - Ordinary temps water has highest surface tension of any liquid except mercury. In ponds cohesion supports organisms
      - Density - Maximum density at 4°C; ice is less dense therefore floats on surface + insulates water beneath, reduces tendency for large bodies of water to freeze completely allowing organisms to survive
- - - - Allows plants to store glucose
      - Made up of a glucose monomers
      - AMYLOSE
        
        Unbranched + coiled, C1-C4 glycosidic bonds
      - AMYLOPECTIN
        
        Branched, C1-C4 + C1-C6 glycosidic bonds
      - Compact + no osmotic effect on cell; doesn't affect water potential of cell
      - Both easily hydrolysed to a glucose, soluble + can be transported to wherever energy is needed
    - - Main storage product in animals
      - Similar structure to amylopectin
      - More branched, C1-C4 + C1-C6 glycosidic bonds
    - - Structural polysaccharide found in plant cell walls
      - Many long, parallel chains of b glucose units
      - Between 60-70 cellulose molecules become tightly cross-linked to form bundles - microfibrils
      - Microfibrils bunched together in bundles to form fibres
      - Unreactive + stable + has high tensile strength
- - - - Double bonds between neighbouring carbon atoms
      - Don't contain maximum possible number of hydrogen atoms
      - If only 1 double bonde between carbon atoms - monosaturated
      - 2 or more double bonds between carbon atoms - polysaturated
      - Double bond forms a kink - unsaturated fatty acids can't be tightly packed together - Not solid
    - - No double bonds between neighbouring carbon atoms in hydrocarbon tail
      - Carries maximum possible number of hydrogen atoms
      - Solid
      - Animal lipids tend to be saturated
      - Possible link between saturated fatty acid + heart disease
      - HEART DISEASE
        
        Main cause - fatty deposits in coronary arteries (atheroscerosis) + high blood pressure (hypertension)
        
        Contributory Factors - Diet high in saturated fatty acids, smoking, lack of exercise + ageing
        
        When food has been absorbed at small intestine, lipids + proteins combine to make lipoproteins, which travel around body in blood stream
        
        If diet is high in saturated fat, low-density lipoproteins build up, fatty material (atheroma) is deposited in coronary arteries, restricting blood flow - oxygen delivery to heart tissue
        
        If diet has high proportion of saturated fats, body make more high-density lipoproteins, carry harmful fats to liver for disposal
        
        Inner wall of artery has a smooth endothelial lining, atheroma is deposited on endothelium, reducing available volume for blood flow, atheroma may completely block artery's lumen
- - - - Sequence of amino acids in polypeptide chain
      - Sequence of amino acid is determined by DNA; 1 gene codes for 1 polypeptide
      - Bond between each amino acid is peptide bond
    - - Shape that polypeptide chain forms due to hydrogen bonding
      - Hydrogen bonds twist + fold polypeptide forming an alpha helix or a less comman beta pleated sheet
    - - Alpha helix of secondary protein structure is further folded + twisted to give a more complex, compact 3D structure
      - Shape is maintained by disulphide, ionic, covalent hydrophobic + hydrogen bonds
      - Enzymes have a tertiary protein structure
      - Bonds maintain shape of enzyme's active site
    - - Structure arises from a combination of 2 or more polypeptide chains in tertiary form
      - Associated with non-protein groups + form large complex molecules, haemoglobin
      - Haemoglobin has 4 polypeptide chains
      - 4 genes are needed to code for haemoglobin; 1 gene for each polypeptide
  - - - Have functions such as enzymes, antibodies, hormones
      - Compact + folded into 3D spherical molecules
      - Soluble in water
      - Haemoglobin; Transports oxygen to body tissues
    - - Perform structural functions
      - Consist of polypeptides in parallel chains or sheets with numerous cross linkages to form long fibres
      - Insoluble in water, strong + tough
      - Collagen provides properties needed in tendons; a single fibre consists of 3 identical polypeptide chains twisted together like a rope
      - These chains are linked by cross-bridges, making a very stable molecule