Q25 - Linking Muscle Molecular Defects to Specific Contraction Abnormalities

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

The following figures illustrate the molecules in muscle fibers in two states: 1. Contraction, 2. Relaxation. The mutation or insufficient function of those molecules are associated with abnormal muscle functions. For example, a mutation in the Ca2+ channel or Acetylcholine receptor (AchR) may cause congenital myopathy. Choices of muscle abnormality: (1) Myopathy (muscle weakness). (2) Difficulties in arm extension. (3) Tetany (involuntary contraction of muscle). (4) Hypercontractility (contraction occurs quickly, but relaxation occurs slowly).

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. Missense mutation in the Tropomyosin binding site of Actin that causes the muscle to be more sensitive for intracellular Ca2+ concentration.

B. Blocking the Ach release by Botulinum toxin treatment.

C. Nonsense mutation in Ca2+ pump gene, which causes a deficiency in the removal of Ca2+ from cytosol.

D. Low blood magnesium level, which results in frequent and uncontrolled depolarization.

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Question reproduced from IBO 2020, Theoretical Exam 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)