DNA and proteins are both polymers found in living organisms. Compare the monomers that make up DNA with the monomers that make up proteins, and state the type of polymerisation used to form each polymer.

AQA A-Level Chemistry (7405) — 3.3.13 Amino acids, proteins and DNA (A-Level only) · Compare · 5 marks · View as Markdown

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

Model answer (5 marks)

The monomers of DNA are nucleotides, whereas the monomers of proteins are amino acids.
DNA contains four different nucleotides (A, T, C, G), whereas proteins are built from a much larger variety of amino acids.
Both DNA and proteins are formed by condensation (dehydration) polymerisation.
In this process each monomer has two reactive functional groups that join together, releasing a small molecule such as water.

Examiner tips

  • Use the exact terms ‘nucleotides’ and ‘amino acids’. Mention the four DNA bases and the many amino acids. State ‘condensation polymerisation’ and explain the loss of water.
  • Keep the answer concise – 5 marks are awarded for a short, accurate comparison.

Mark scheme (5 marks)

  1. The monomers of DNA are nucleotides
  2. The monomers of proteins are amino acids
  3. DNA is made from four different nucleotides (whereas proteins use many different amino acids) OR a correct comparative statement about monomer variety
  4. Both DNA and proteins are formed by condensation polymerisation
  5. Condensation polymerisation involves monomers with two functional groups joining together and losing small molecules such as water

Key terms in this question

DNA

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