DP Biology (last assessment 2024)

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Question 22N.2.SL.TZ0.7b

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Date November 2022 Marks available [Maximum mark: 5] Reference code 22N.2.SL.TZ0.7b
Level SL Paper 2 Time zone TZ0
Command term Describe Question number b Adapted from N/A
b.
[Maximum mark: 5]
22N.2.SL.TZ0.7b

Humans ingest food which provides energy and nutrients to carry out life processes.

(b)

Describe how the small intestine is adapted for efficient absorption of nutrients.

[5]

Markscheme
  1. small intestine is very long;
  2. small intestine contains villi/microvilli;
  3. the epithelial cells of villi have microvilli;
  4. these increase the surface area for absorption;
  5. the cells of the small intestine contain (a large number of) mitochondria;
  6. these provide energy for active transport;
  7. the walls contain proteins for active transport/ facilitated diffusion;
  8. the villi have a rich blood supply/ lacteals;
  9. the walls of the villi are thin so less distance for diffusion;
Examiners report

In (b) most gained two marks for correctly mentioning villi and that they increase the SA. A common misconception was that the villi were sort of 'stuck on', rather than being foldings. There were a lot of vague answers about position of the rich blood supply and lacteals as being in the small intestines rather than in the villi themselves. The question was about efficient absorption, therefore references to the longitudinal and circular muscles were superfluous.

Syllabus sections