Question

Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction

• A. Sodium.
• B. Potassium.
• C. Calcium
• D. Magnesium

Answer 1

Calcium is the ion responsible for the unmasking of active sites for myosin for cross-bridge activity during muscle contraction. Nervous stimulation causes a depolarisation of the muscle membrane (sarcolemma) which triggers the release of calcium ions from the sarcoplasmic reticulum. Calcium ions bind to troponin, thus causing tropomyosin to shift from the face of the actin filament to which myosin heads need to bind to produce contraction.