Describe how lactase is used to produce lactose-free milk, and explain why this product is beneficial to some people.

Cambridge International IGCSE Biology (0610) — 21.2 Biotechnology · Describe and Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Lactase is added to the milk and mixes with it.
The enzyme hydrolyses lactose into glucose and galactose.
The resulting milk can be consumed by people who are lactose intolerant.
Lactose‑intolerant people lack or cannot produce sufficient lactase, so they cannot digest lactose themselves.

Examiner tips

Use the exact phrase "lactase is added to the milk" to gain the first point. Show the chemical reaction: lactose → glucose + galactose. Mention the benefit directly: it can be consumed by lactose‑intolerant people. Explain the cause: lack of lactase production.

Common mistakes

Writing "lactase is mixed into the milk" instead of "added to the milk". Forgetting to state the hydrolysis products. Omitting the explanation of why lactose‑intolerant people cannot digest lactose.

Mark scheme (4 marks)

Lactase is added to / mixed with milk
Lactase breaks down / digests lactose into glucose and galactose
The resulting milk can be consumed by people who are lactose intolerant
Lactose-intolerant people lack / cannot produce sufficient lactase (so cannot digest lactose themselves)

Key terms in this question

lactase · lactose · lactose-free milk