DP Biology (last assessment 2024)

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Question 22M.2.HL.TZ1.5d

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Date May 2022 Marks available [Maximum mark: 3] Reference code 22M.2.HL.TZ1.5d
Level HL Paper 2 Time zone TZ1
Command term Explain Question number d Adapted from N/A
d.
[Maximum mark: 3]
22M.2.HL.TZ1.5d

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.]

(d)

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.

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