Question

question 5 (1.25 points)
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for the sliding filament model to work,

1. acetylcholine is released and the sarcomere shortens
2. tropomyosin breaks down to troponin, resulting in muscle contraction
3. atp is produced and it binds to actin
4. ca²+ binds to troponin, resulting in shifting of tropomyosin
5. ca²+ binds to tropomyosin, and the sarcomere relaxes

Explanation:

• In the sliding filament model:
• Acetylcholine release is the start of muscle contraction signaling but alone doesn't directly make the sarcomere shorten in the context of the sliding mechanism details.
• Tropomyosin doesn't break down to troponin. They are different regulatory proteins.
• ATP binds to myosin, not actin, for the cross - bridge cycle.
• When \(Ca^{2+}\) binds to troponin, it causes a conformational change that shifts tropomyosin, uncovering the myosin - binding sites on actin, which is crucial for the sliding of filaments (actin and myosin) in muscle contraction.
• \(Ca^{2+}\) binding to tropomyosin is not the correct regulatory step for the sliding filament model (it binds to troponin), and when \(Ca^{2+}\) is removed (not when binding in the wrong way), the sarcomere relaxes.

Answer:

1. \(Ca^{2+}\) binds to troponin, resulting in shifting of tropomyosin