Biological Molecules

Polymerisation
1. Molecules linking to one another to form polymers
  1. Condensation reactions = joining 2 monomers and removing a water in the process
  2. Hydrolysis = breaking down units by the addition of water
Carbohydrates
1. Monosaccharides with the formula C6H1206 (glucose, fructose and galactose)
  1. All monosaccharide's are reducing sugars, test for this by Benedicts test
    1. semi -quantitative, insoluble red precipitate of copper oxide is formed if present.
    2. testing for non-reducing sugars, add HCl to hydrolyse any bonds and then add NaOH to neutralise. Then do the reducing sugar test
  2. monosaccharide's combined form disaccharides and polysaccharides
    1. joined by glycosidic bond
    2. Disaccharides
      1. glucose + glucose = maltose
      2. glucose + fructose = sucrose
      3. glucose + galactose = lactose
    3. Polysaccharides
      1. Starch
        Test for starch = add iodine solution and blue/black colour present
        Major energy source in plants
        Made of chains of a- glucose, branched/unbranched wound into tight coils
        insoluble so doesn't affect water potential.
        easily hydrolysed so can be transported quickly
        branched form has many ends for rapid enzyme action
        compact so lots can be stored
      2. Cellulose
        made up of B- glucose
        straight, unbranched chains than run parallel to each other so hydrogen bonds can form (microfibrils)
        hydrogen bonds form cross links across parallel strands
        Adds strength and rigidty
        Prevents cell bursting from water entering by osmosis as exerts an inward pressure
      3. Glycogen
        major energy storage source in animals and bacteria
        insoluble so doesn't affect water potential
        doesn't diffuse out of cells due to it being compact
        more branched and shorter than starch for rapid enzyme action
        animals have higher metabolic rate than plants, so is important
Lipids
1. insoluble yet soluble in organic solvents
2. Triglycerides
  1. 3 Fatty acids with 1 glycerol (joined by ester bond)
    1. Saturated Fatty acids = no carbon-carbon double bonds
    2. Unsaturated fatty acids = carbon-carbon double bonds
      1. double bonds cause the molecule to bend, therefore cannot pack and so is a liquid
  2. low mass to energy ratio
  3. insoluble so don't affect osmosis or water potential
  4. lots of oxygen-hydrogen bonds and so release water when oxidised
3. Roles: -cell membranes, source of energy, waterproofing, insulation (electrical and heat)
  1. Test for lipids//emulsion test = add ethanol, shake to dissolve. Then add water and shake. Cloudy white colour if present.
4. Phospholipids
  1. 2 fatty acids, phosphate and glycerol
  2. Hydrophobic fatty acid tail- repel water
  3. Hydrophilic head - interacts with water
    1. 2 different parts = polar molecule
  4. when in water, the molecules form a bilayer (cell surface membrane).
    1. Form glycolipids by combining carbohydrates
Water
1. Oxygen slightly negative , Hydrogen slightly positive
  1. Water molecules get attracted to each others components due to opposite charges and a hydrogen bond forms
2. high specific heat capacity
  1. hydrogen bonds present means more energy needed to break molecules apart
  2. Acts as a buffer for sudden temp changes
3. Latent heat of vapourisation
  1. Lot of energy to evaporate water
    1. Sweat is effective in cooling down as energy used to evaporate water and release heat out of body
4. Cohesion
  1. Hydrogen bonding means that molecules stick together and can be pulled up xylem
5. Metabolism
  1. water used for hydrolysis/condensation
  2. Water dissolves gases
  3. Water transparent so aquatic animals can photosynthesise

Next up

Biological Molecules

Description

Resource summary

Similar

	Created by Ella Cannings over 10 years ago