Glucose is a monomer. Explain how glucose monomers are used to build a polymer, and state two different polymers that can be formed from glucose monomers 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)

Glucose monomers are joined together to form a polymer.
They are linked by condensation reactions.
During each condensation reaction a molecule of water is released.
One polymer that can be formed is starch (or glycogen).
Another polymer that can be formed is cellulose (or glycogen or starch, different from the first).

Examiner tips

Use the phrase ‘joined together’ and ‘condensation reactions’ – these are the exact words the mark scheme looks for.
Show that water is released in each step – this demonstrates understanding of the reaction type.
Name two distinct polymers – avoid repeating the same polymer twice.
Keep the answer concise – 5 marks can be earned with 5 short points.

Common mistakes

Writing ‘glucose is polymerised’ instead of ‘joined together’ – wording is not credited.
Forgetting to mention that water is released – a key point in the scheme.
Naming the same polymer twice (e.g., starch twice) – only one distinct polymer is awarded.

Mark scheme (5 marks)

Glucose monomers are joined together (to form a polymer)
By condensation reactions (to form the polymer chain)
Water is released / removed during the reaction
First correct polymer named — starch OR glycogen
Second correct polymer named — cellulose OR glycogen OR starch (different from first answer)

Key terms in this question

monomer · polymer · glucose