If a muscle fiber were to suddenly and permanently stop producing ATP the fiber would no longer be able to actively transport ca

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If a muscle fiber were to suddenly and permanently stop producing ATP the fiber would no longer be able to actively transport ca

lcium out of the cytoplasm (sarcoplasm) and the intracellular calcium concentration would rise. Which of the following would you expect to happen? A. Calcium would be transported to the sarcoplasmic reticulum therefore contractions would cease. B. Myosin would be able to bind to the exposed binding sites on thin filaments but it would not be able to detach. C. The fiber would twitch uncontrollably due to excessive calcium bound to troponin. D. No change would occur in a muscle that was relaxed to begin with.

Biology

1 answer:

enyata [2.5K] · Answer 1 · 2026-03-24T23:01:16+03:00

A. Calcium would be sent to the sarcoplasmic reticulum, causing contractions to stop. A muscle fiber ceases to contract the instant ATP is depleted. Furthermore, contraction halts when signals from the motor neuron stop, leading to the repolarization of the sarcolemma and T-tubules, thus closing the voltage-gated calcium channels in the sarcoplasmic reticulum. Calcium ions are subsequently pumped back into the sarcoplasmic reticulum, allowing tropomyosin to once again obstruct the binding sites on the actin filaments.

If a muscle fiber were to suddenly and permanently stop producing ATP the fiber would no longer be able to actively transport ca

b) Anaphase II of meiosis