Biology Support & Movement MDCAT 2019
PMDC Verified Question 67 of 75
Thin filaments of muscles contain ____ chains of actin molecules.
A
Four
B
Three
C
One
D
Two
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Two
Concept:

Molecular composition of the thin myofilament.

Formula:

N/A (Conceptual)

Solution:

  • The core of the thin filament is composed of the protein F-actin (filamentous actin).


  • F-actin is formed by the polymerization of globular G-actin monomers into exactly two long strands that twist around each other in a double-helical configuration.


Why other options are incorrect:

While thin filaments also contain tropomyosin and the 3-subunit troponin complex, the foundational actin core strictly consists of only two intertwined chains.

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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