Muscle contraction is a chemical process involving proteins. Explain how skeletal muscle contracts.

The best way to approach these type of questions (worth 8 marks) is to explain everything step by step. This will make it much easier for you to explain under stressful exam situations as well as for the examiner to understand your thought process.

1 - An action potential reaches the end of the motor neuron, triggering the release of Ca to be released from the sarcoplasmic reticulum.

2 - the Ca ions bind to proteins called troponin, which are attached to the tropomyosin proteins of the thin actin filaments of the sarcomere

3 - tropomyosin reveals its binding site on the thin actin filaments

4 - myosin heads of the thick myosin filaments attach to the binding sites on actin, resulting in a cross-bridge

5 - ATP on the myosin heads is hydrolysed, releasing ADP and phosphate

6 - myosin head cocks toward the sarcomere centre - this is called a power stroke

7 - another ATP molecule binds to the myosin head, breaking the cross bridge between myosin heads and actin

8 - the whole process is repeated

Answered by Hilary L. Biology tutor

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