DP Biology (first assessment 2025)

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Question 22N.2.SL.TZ0.2a

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Date November 2022 Marks available [Maximum mark: 2] Reference code 22N.2.SL.TZ0.2a
Level SL Paper 2 Time zone TZ0
Command term Annotate Question number a Adapted from N/A
a.
[Maximum mark: 2]
22N.2.SL.TZ0.2a
(a)

Annotate the diagram to illustrate the amphipathic nature of phospholipids.

[2]

Markscheme
  1. line to circle labelled phosphate (head) and (tail) labelled fatty acid/hydrocarbon/lipid (tail);
  2. label hydrophilic/polar/attracted to water/ and hydrophobic/non polar/not attracted to water;
Examiners report

Part (a) was a variation on a classic Section B question on the phospholipid bilayer. Approximately 1 in 10 students left it blank, suggesting that many did not think that they had to reply to it as there was no answer box. Cholesterol's function in reducing fluidity and permeability was not well known in (b). In (c) poorer candidates described endosymbiosis, rather than answering the question. Many knew about double membranes, own DNA and 70s ribosomes, but did not score any marks as they failed to say that they were in mitochondria and/or chloroplasts. This is perhaps a case where planning the answer was lacking, rather than rushing in.

Syllabus sections