Describe the roles of proteins and lipids as biological molecules in living organisms.

Pearson Edexcel International GCSE Biology (4BI1) — 2.3 Biological molecules · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Proteins are large molecules made up of amino acids.
They perform structural or functional roles, such as enzymes, antibodies, muscle tissue and haemoglobin.
Lipids are composed of fatty acids and glycerol.
They serve as an energy store, provide insulation and form the lipid bilayer of cell membranes.

Examiner tips

  • Use the exact terms ‘amino acids’, ‘enzymes’, ‘antibodies’, ‘fatty acids’, ‘glycerol’, ‘energy store’, ‘insulation’, ‘cell membranes’. Separate each point clearly to match the four marks. Include both structural and functional examples for proteins.
  • common_mistakes
  • :
  • Confusing lipids with carbohydrates. Omitting the fatty acid/glycerol composition of lipids. Using vague terms like ‘important’ instead of specific functions.

Mark scheme (4 marks)

  1. Proteins are large molecules made up of amino acids
  2. Proteins have a structural or functional role, e.g. enzymes / antibodies / muscle / haemoglobin
  3. Lipids are made from fatty acids and glycerol
  4. Lipids serve as an energy store / provide insulation / make up cell membranes

Key terms in this question

proteins · lipids

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