Describe what is meant by a monomer and a polymer, and describe how polymers can be broken down in living organisms.

AQA A-Level Biology (7402) — 3.1.1 Monomers and Polymers · Describe · 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 molecule that acts as a repeating unit or building block.
A polymer is a large molecule made up of many monomers joined together.
Polymers are broken down in living organisms by hydrolysis.
During hydrolysis, water molecules are used to break the bonds between monomers.
The process releases or produces the original monomers from the polymer.

Examiner tips

Use the exact terms ‘monomer’, ‘polymer’, and ‘hydrolysis’. Show the sequence: monomer → polymer → hydrolysis → monomer. Include that water is used in the reaction.
Include that hydrolysis is a type of chemical reaction that cleaves covalent bonds.

Common mistakes

Confusing ‘polymerisation’ with ‘hydrolysis’. Omitting the role of water in the reaction. Using vague terms like ‘break down’ without specifying hydrolysis.

Mark scheme (5 marks)

A monomer is a small molecule that is a repeating unit / building block
A polymer is a large molecule made up of many monomers joined together
Polymers are broken down by hydrolysis
Water molecules are used / added to break the bonds between monomers
Hydrolysis releases / produces monomers from the polymer

Key terms in this question

monomer · polymer