Explain why glucose molecules are able to move from the small intestine into the blood even when the concentration of glucose in the blood is higher than in the small intestine.

Edexcel GCSE Biology (1BI0) — 1.5 Transport in cells · Explain · 4 marks · View as Markdown

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

After a meal, glucose is absorbed from the small intestine into the bloodstream. This process continues even when the concentration of glucose in the blood is already higher than in the small intestine.

Model answer (4 marks)

Active transport

Glucose is moved against its concentration gradient from the small intestine into the blood.

The transport requires energy, supplied by cellular respiration.

Carrier (transporter) proteins in the intestinal cell membrane carry the glucose into the bloodstream.

Examiner tips

  • Use the word 'active transport' and mention it moves against the gradient. Include that energy from respiration is needed. State that carrier proteins in the membrane are involved.
  • common_mistakes
  • :
  • Confusing passive diffusion with active transport. Forgetting to mention the energy source or carrier proteins. Using the wrong term for the transport mechanism.

Mark scheme (4 marks)

  1. The process used is active transport
  2. Movement is against / up the concentration gradient
  3. The process requires energy (from respiration)
  4. Carrier proteins / transporter proteins in the cell membrane are used to move the glucose molecules

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