Starch, proteins and DNA are all examples of polymers found in living organisms. Explain what is meant by the terms 'monomer' and 'polymer', and name one monomer that makes up each of the three polymers listed.

AQA A-Level Biology (7402) — 3.1.1 Monomers and Polymers · Explain · 5 marks · View as Markdown

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

Model answer (5 marks)

A monomer is a small, single molecule that is the building block of a polymer.
A polymer is a large molecule made of many monomers joined together.
The monomer of starch is glucose.
The monomer of proteins is an amino acid.
The monomer of DNA is a nucleotide.

Examiner tips

  • Use the exact terms ‘monomer’ and ‘polymer’ as defined in the mark scheme.
  • Give the correct monomer for each polymer – glucose, amino acid, nucleotide.
  • Keep the answer concise and avoid extra explanation to stay within the 5‑mark limit.

Common mistakes

  • Confusing monomer with polymer or vice‑versa.
  • Listing the wrong monomer (e.g. ribose for DNA instead of nucleotide).
  • Adding unnecessary detail such as polymer structure or function.

Mark scheme (5 marks)

  1. A monomer is a small / single molecule that is the building block of a polymer
  2. A polymer is a large molecule made of many monomers joined together
  3. Glucose is the monomer of starch
  4. Amino acids are the monomers of proteins
  5. Nucleotides are the monomers of DNA

Key terms in this question

monomer · polymer · starch · protein · DNA

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