HL 1 Biology

3.2 Organic Molecules

<<Organic and Inorganic Compounds>>

*Chemistry of living things is based on the element carbon.
  • Organic: any compounds consisting carbon that are found in living organisms
      • e.g carbohydrates, lipids and proteins
      • e.g. of organic chemicals that are not in living things: plastics and petrol
  • Inorganic: compounds that contain no carbon
      • e.g carbon dioxide, carbonates and hydrogen carbonates
  • **Structural formulas:show atoms in a compound & way atoms are bound to each other
      • covalent bond: straight line
      • condensed structural formulas: hydrogen+ other atom bonds omitted because its easy to predict

Macromolecules: large molecules that results from assembling long chains of repeating subunits (monomers)

  • e.g Nucleic acid RNA: made up of a long chain of individual nucleotides
  •  Polypeptide: consists of a long chain of amino acids

<<Condensation and Hydrolysis>>

Condensation: process in which subunits combine/water removed

  • *subunits of polysaccharides, polypeptides and nucleic acids are monosaccharides, amino acids and nucleotides
  • involves a loss of an -OH from one molecule and an -H from another molecule (which together form H2O)
  • involves combination of subunits and yields water

Hydrolysis: reaction in which water is added in to split the bonds formed by condensation

  • e.g. disaccharide can be split, using water, into two monosaccharides
  • polypeptides + water ——> dipeptides/amino acids
  • polysaccharides + water –> disaccharides/monosaccharides
  • glycerides + water ———> fatty acids + glycerol

<<Lipids and Carbohydrates>>

Carbohydrates: composed of carbon, hydrogen and oxygen with hydrogen and oxygen in a ratio of 2H:1 O

  • monosaccharides: sub-units/monomers of carbohydrates
      • e.g. ribose
      • glucose – energy source in animal cells, transport energy
      • fructose – component of flower nectar, used to make fruits sweet-tasting
      • galactose
  • disaccharides:
      • e.g. maltose
      • lactose – sugar in milk that provides energy to young mammals
      • sucrose – transport form of carbohydrates in phloem, to transport energy to cells in plants
  • polysaccharides: carbohydrates with many monomers
      • e.g. starch
      • glycogen – carbohydrate storage in liver and muscles f animals
      • cellulose- component of plant cell wall

Lipids: broad category of molecules including steroids, waxes, fatty acids and triglycerides

  • triglycerides= in room temperature fats if solid or oil if liquid
      • formed by combination of 3 fatty acids with one molecule of glycerol
      • then three water molecules produced (condensation reaction)
      • breakdown of triglycerides occur by hydrolysis
      • serve as insulation or store energy
  • Functions of lipids:
      • Energy storage – form of fat in humans, oil in plants
      • Heat insulation- fat under skin reduces heat loss
      • Buoyancy – lipids are less dense than water; helps animals float
  • Lipids + Carbohydrates both used for energy storage.
  • Lipids: have twice more energy per gram than carbohydrates
  • Carbohydrates: more soluble thus easier to transport. But tend to have a stronger impact on osmotic balance


Emperor Penguins (pg. 50)

1a) (i) wild: 37.2-23.9 =  13.3 kg

(ii) captive: 38.6 – 22.4 = 16.2 kg

b) Although both groups of birds have lost parts of their lipid, the captive birds showed a larger decrease in their lipids compared to the wild birds. The wild birds lost 81% whereas the captive birds showed a loss of 93%.

c) The insulation may be another important factor for penguin survival.


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