Explain how the liver and gallbladder work together in the digestion of lipids. Refer to the tissues and organs involved in your answer.

AQA GCSE Biology (8461) — 4.2.2 Animal tissues, organs and organ systems · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Bile is produced by the hepatocytes of the liver and secreted into the bile ducts.
The bile is carried via the common hepatic duct to the gallbladder where it is stored and concentrated.
When a fatty meal enters the duodenum, the gallbladder contracts and releases bile into the small intestine.
Bile contains bile salts that emulsify large fat globules into many small droplets, increasing the surface area for pancreatic lipase to act on, thereby accelerating lipid digestion.

Examiner tips

  • Use the exact terms ‘hepatocytes’, ‘bile ducts’, ‘common hepatic duct’, ‘gallbladder’, ‘bile salts’, ‘emulsify’, and ‘lipase’. Show the sequence: liver → bile ducts → gallbladder → duodenum. Explain the effect of increased surface area on lipase activity.
  • common_mistakes
  • :
  • Confusing bile production with bile secretion; failing to mention the gallbladder’s storage role. Using vague terms like ‘digestive juice’ instead of ‘bile salts’. Omitting the link between emulsification and increased lipase activity.

Mark scheme (4 marks)

  1. Bile is produced in the liver
  2. Bile is stored in the gallbladder
  3. Bile emulsifies fats / lipids (breaks them into smaller droplets)
  4. This increases the rate of digestion of lipids by lipase (by increasing surface area)

Key terms in this question

liver · gallbladder

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