A-Level Biology AQA Notes

3.1.3 Lipids

Lipids
  • Fatty acids can be:
    • Saturated – there are no C=C bonds and the molecule has as many hydrogen atoms as possible.
    • Unsaturated – there is at least one C=C bond, therefore the molecule contains fewer hydrogen atoms than is maximally possible.
  • A triglyceride molecule is formed by joining one molecule of glycerol to three fatty acids through three condensation reactions, forming ester bonds.
  • Triglycerides have key roles in respiration and energy storage due to its insolubility and high carbon to hydrogen ratio.
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  • Phospholipids replace one of the fatty acid chains in triglycerides with a phosphate molecule.
  • The hydrophobic tails and hydrophilic heads of phospholipids allow them to form phospholipid bilayers.
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