Biology Support & Movement SZABMU 2022
PMDC Verified Question 61 of 75
The muscle contraction involves the breakdown of cross bridges of actin and myosin filaments due to the following process:
A
ATP is oxidized
B
ATP is reduced
C
ATP is hydrolyzed
D
ATP is synthesized
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: ATP is hydrolyzed
Concept:

The cross-bridge cycle and ATP utilization.

Formula:

$$ATP + H_2O \rightarrow ADP + P_i + Energy$$

Solution:

  • In the cross-bridge cycle, the physical binding of a new ATP molecule to the myosin head causes it to detach (break) from actin.


  • Immediately following detachment, the myosin head acts as an enzyme, hydrolyzing the ATP into ADP and inorganic phosphate (\(P_i\)).


  • This hydrolysis reaction releases the energy required to cock the myosin head back into its high-energy, ready-to-fire position.


Why other options are incorrect:

ATP is not fundamentally oxidized or reduced in this mechanical step; it strictly undergoes enzymatic hydrolysis (cleaving a phosphate bond with water).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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