If Ca2+ were suddenly removed from a contracting skeletal...

If Ca2+ were suddenly removed from a contracting skeletal muscle fiber while ATP remained available, what would happen most immediately?

hard

AMyosin would keep cycling normally because Ca2+ is not needed once contraction begins

New cross-bridges would stop forming because tropomyosin would re-cover binding sites, and the muscle would relax

CATP would instantly disappear

DThe A band would shorten

EThe myosin filaments would disassemble

Explanation

Ca2+ is required to keep actin binding sites exposed. If Ca2+ falls, tropomyosin blocks binding, cross-bridge cycling stops, and the muscle relaxes (as attached bridges finish and detach).

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Source: entermedschool.org

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