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IGCSE · Practice questions · Absorption

More surface, faster uptake.

Six original Cambridge-style questions on absorption in the small intestine and colon, villus structure, surface area and the roles of capillaries and lacteals.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Two routes out of a villus.

01
Recall
[2 marks]

State where in the alimentary canal (a) nutrients are absorbed and (b) water is absorbed.

  • (a) The small intestine. ✓
  • (b) Most water in the small intestine; some in the colon. ✓
02
Recall
[4 marks]

Extended. Describe the structure of a villus.

  • A finger-like projection (about 1 mm long) of the lining of the small intestine. ✓
  • Covered by an epithelium one cell thick, whose cells have microvilli. ✓
  • Contains a dense network of blood capillaries. ✓
  • With a lacteal (lymph vessel) in the centre. ✓
03
Explain
[3 marks]

Extended. Explain the significance of villi and microvilli in the small intestine.

  • Villi and microvilli greatly increase the internal surface area of the small intestine. ✓
  • So more molecules of digested food can be absorbed at the same time. ✓
  • Absorption is faster and more complete before the food leaves the small intestine. ✓
04
Explain
[4 marks]

Extended. Describe the roles of the capillaries and the lacteal in a villus.

  • Capillaries absorb glucose and amino acids (and water and ions). ✓
  • The blood carries them away to the liver, keeping the concentration gradient steep. ✓
  • The lacteal absorbs fatty acids and glycerol. ✓
  • They are carried away in the lymph, which later drains into the blood. ✓
05
Calculation
[3 marks]

Extended. A 1 cm2 area of flat intestine lining is folded into villi, which multiply the area by 10. The epithelial cells carry microvilli, which multiply the area by a further 20. (a) Calculate the final surface area. (b) A section of small intestine has a flat lining area of 2000 cm2. Calculate its absorbing surface area in m2. (1 m2 = 10 000 cm2)

  • (a) 1 × 10 × 20 = 200 cm2. ✓
  • (b) 2000 × 200 = 400 000 cm2. ✓
  • 400 000 ÷ 10 000 = 40 m2. ✓
06
Analysis
[3 marks]

Extended. Coeliac disease damages the villi so that they become short and flattened. Suggest and explain why people with untreated coeliac disease may lose body mass even though they eat a normal diet.

  • Flattened villi (and fewer microvilli) give a much smaller internal surface area. ✓
  • So fewer digested nutrients such as glucose, amino acids, fatty acids and glycerol are absorbed into the blood and lymph. ✓
  • Less energy and fewer raw materials reach the cells, so body stores are used up and mass is lost; more food leaves in the faeces. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.