F212 - Biological Molecules

Water
1. Water is a polar molecule.
  1. It can form hydrogen bonds
2. Properties of Water
  1. Solvent
    1. Metabolic processes rely on chemicals being able to react together
  2. Liquid
    1. Movement of materials requires a liquid transport medium
  3. Cohesion
    1. creates surface tension and makes long, thin water columns very stong
3. More Properties of Water
  1. Freezing
    1. Water below a frozen surface becomes insulated and less likely to freeze
  2. Thermal Stability
    1. Large bodies of water have fairly stable temperatures. Evaporation of water can col surfaces by removing heat
  3. Metabolic
    1. Water takes part as a reactant in some processes.
Proteins
1. Amino Acids
  1. Structure
  2. Peptide Bonds
    1. Synthesis
      1. The –OH from one amino acid and the –H from another are removed to make water, and the C and the N join together via a peptide bond
    2. Hydrolysis
      1. A water molecule is used to break the peptide bond. The –H joins back to the N, and the –OH back to the C
2. Structure of Proteins
  1. Primary
    1. The unique sequence of amino acids
  2. Secondary
    1. Coiling of pleating parts of the polypeptide
      1. β-pleated sheet
      2. α-helix
  3. Tertiary
    1. overall '3D' structure
      1. Hydrogen Bonding, Ionic Bonding, Hydrophobic Bonds, Disulfide Bridges
  4. Quarternary
    1. more than one polypeptide chain
      1. e.g. Haemoglobin - four polypeptide chains
3. Collagen
  1. Three polypeptide chains with hydrodgen bonds and cross links - the cross links are staggered to make the molecule stronger.
4. Haemoglobin vs. Collagen
Carbohydrates
1. Glucose
  1. Alpha / Beta
    1. OH below plane / OH above plane
2. Glycosidic Bonds
  1. Synthesis
    1. The –OH from one glucose and the –H from another are removed to make water, and the O and the C join together via a glycosidic bond
  2. Hydrolysis
    1. A water molecule is used to break the glycosidic bond. The –H joins back to the O, and the –OH back to the C4
3. Amylose vs. Cellulose
4. Structure of Glycogen
  1. Mostly 1,,4/ 9% are 1,6
5. Relating Structure to Function
  1. Glucose
    1. Simplest sugar - used in respiration
  2. Amylose
    1. insoluble in water - doesn't affect ψ
  3. Glycogen
    1. Many branches means it can be hydrolysed easily
  4. Cellulose
    1. very strong and arrangement of macrofibrils allows water to move in and out easily and determines how a cell can grow or change shape
  5. Triglyceride
    1. compact energy store, insoluble in water - doesn't affect ψ
  6. Cholseterol
    1. Small, thin molecules - fit into the lipid bilayer giving strength and stability
  7. Phospholipid
    1. Part hydrophilic/part hydrophobic - idea for cell membranes
6. Triglyceride
  1. Glycerol,three fatty acids
7. Phospholipid
  1. Glycerol , two fatty acids ,phosphate
Colorimetry
1. Chemical Tests
  1. protein (biuret) test
    1. pale blue to lilac
  2. reducing sugars - Benedict's test
    1. add Benedict’s, heat to 80˚C - blue to orange-red
  3. non-reducing sugars - Benedict's test
    1. If RS is - boil with HCl, cool and neutralise with NaHCO3. repeat Benedict’s test.
  4. starch (iodine) test
    1. yellow to blue-black
  5. lipids (emulsion) test
    1. Mix the ethanol, pour into water - emulsion forms if a lipid is present
2. Determining concentration of glucose in a solution
  1. Perform Benedict's test on the solution until there is no further colour change.
    1. Cool and filter solution
      1. Take filtrate and test using a colorimeter
        Low reading for absorbance means higher conc. of reducing sugar.
        High reading for absorbance means lower conc. of reducing sugar

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F212 - Biological Molecules

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	Created by katy stopforth about 9 years ago