Explain how a polymer is formed from monomers, and why this process is important in living organisms.

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)

Monomers are small, single molecules that act as the building blocks of polymers.

Monomers are joined together by covalent chemical bonds to form a polymer.

The process of joining monomers to form a polymer is called polymerisation.

A polymer is a long chain or large molecule made of many repeating monomer units.

Polymers are important because large biological molecules such as DNA, proteins and carbohydrates are polymers that carry out essential functions in living organisms.

Examiner tips

Use the exact terminology: monomers, polymerisation, polymer, covalent bonds.
Show the sequence: monomers → covalent bonds → polymerisation → polymer.
Explain the biological relevance: DNA, proteins, carbohydrates.
Keep the answer concise and to the point.

Common mistakes

Using non‑covalent bonds (e.g., hydrogen bonds) instead of covalent bonds for polymerisation.
Omitting the term ‘polymerisation’ or confusing it with ‘depolymerisation’.
Failing to mention the biological examples (DNA, proteins, carbohydrates).

Mark scheme (5 marks)

Monomers are small/single molecules that are the building blocks of polymers
Monomers are joined together by chemical bonds to form a polymer
The process of joining monomers to form a polymer is called polymerisation
A polymer is a long chain/large molecule made of many repeating monomer units
Polymers are important because large biological molecules (such as DNA, proteins, or carbohydrates) are polymers that carry out essential functions in living organisms

Key terms in this question

monomer · polymer