DP Biology (last assessment 2024)

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Question 22M.2.HL.TZ1.d

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Date May 2022 Marks available [Maximum mark: 3] Reference code 22M.2.HL.TZ1.d
Level HL Paper 2 Time zone TZ1
Command term Explain Question number d Adapted from N/A
d.
[Maximum mark: 3]
22M.2.HL.TZ1.d

The diagram shows a section through part of the leg of an insect and antagonistic muscles X and Y. The tibia moves in the direction shown by the arrow when the muscle is flexing.

[Source: D G Mackean www.biology-resources.com.]

Explain the role of calcium ions in muscle contraction.

[3]

Markscheme
  1. calcium released from sarcoplasmic reticulum;
  2. calcium binds to troponin;
  3. causes tropomyosin to move;
  4. uncovers binding sites;
  5. myosin heads bind to the actin forming cross bridges;
Examiners report

Well prepared candidates had no difficulty in describing the role of calcium in muscle contraction but they were in the minority. The discrimination index was very high.

Syllabus sections