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Multiple Choice
What are the functional units of contraction in a muscle fiber called?
A
Sarcomeres
B
Mitochondria
C
T-tubules
D
Myofibrils
Verified step by step guidance
1
Understand that the question is asking about the functional units of contraction in a muscle fiber, which refers to the smallest structural and functional unit responsible for muscle contraction.
Recall that muscle fibers are composed of myofibrils, which are long, cylindrical structures containing repeating units called sarcomeres. Sarcomeres are the actual functional units of contraction.
Learn that sarcomeres are made up of thick filaments (myosin) and thin filaments (actin), which slide past each other during contraction, shortening the sarcomere and thus the muscle fiber.
Differentiate between the other options: Mitochondria are organelles responsible for energy production, T-tubules are involved in transmitting electrical signals, and myofibrils are bundles of sarcomeres but not the functional unit themselves.
Conclude that the correct answer is 'Sarcomeres,' as they are the smallest units within myofibrils responsible for contraction in muscle fibers.