Describe the role of bile in the digestion of lipids in the human digestive system.

Pearson Edexcel International GCSE Biology (4BI1) — 2.6 Nutrition: humans · Describe · 4 marks · View as Markdown

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

Lipids are a group of large molecules made from fatty acid chains and glycerol. Before lipase can act efficiently on lipids, bile plays an important preparatory role in the duodenum.

Model answer (4 marks)

Bile is produced in the liver and stored in the gallbladder.
Bile emulsifies fats, breaking large lipid droplets into smaller ones.
The increased surface area of the emulsified droplets allows pancreatic lipase to act more efficiently.
Bile also neutralises the acidic chyme from the stomach, creating a suitable pH for lipase activity.

Examiner tips

  • Use the exact terms "bile", "emulsifies", "surface area", "neutralises"
  • Show the sequence: production → emulsification → surface area increase → pH neutralisation
  • Keep answer concise, 4 points total

Common mistakes

  • Confusing bile with pancreatic enzymes
  • Forgetting that bile is stored in the gallbladder
  • Not mentioning the pH change in the duodenum

Mark scheme (4 marks)

  1. Bile is produced in the liver (and stored in the gallbladder)
  2. Bile emulsifies fats / lipids
  3. Emulsification increases the surface area of lipid droplets available for lipase to act on
  4. Bile neutralises stomach acid in the duodenum, providing a suitable pH for lipase to work

Key terms in this question

bile · lipids

Related

More Nutrition: humans questions

▶ Try answering this question with AI marking (free) →