Biology Support & Movement MDCAT 2019
PMDC Verified Question 68 of 75
The thick filaments in a myofibril of muscles are made up of ____.
A
Haemoglobin
B
Actin
C
Myoglobin
D
Myosin
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Myosin
Concept:

Protein composition of muscle filaments.

Formula:

N/A (Conceptual)

Solution:

  • Myofibrils contain two main types of filaments: thick and thin.


  • The thick filaments are composed entirely of hundreds of intertwined molecules of the motor protein myosin, which features heavy tail regions and specialized globular heads with ATPase activity.


Why other options are incorrect:

Actin forms the thin filaments. Haemoglobin and myoglobin are entirely separate globular oxygen-binding proteins, completely unrelated to the physical filament structure.

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