Multiple Choice
Which of the following structures is composed of actin, but no myosin?
15. Cytoskeleton and Cell Movement
Muscle Contractions
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Which of the following is not a structure of the sarcomere?
A
A band
B
H zone
C
Z line
D
U zone
Verified step by step guidance1
Understand the structure of a sarcomere: A sarcomere is the basic contractile unit of muscle fiber, composed of repeating sections of actin and myosin filaments.
Identify the key components of a sarcomere: The main structures include the A band, I band, H zone, Z line, and M line.
Define each component: The A band contains the entire length of the thick filaments (myosin), the H zone is the central part of the A band where there is no overlap with thin filaments, and the Z line marks the boundary between adjacent sarcomeres.
Recognize that the 'U zone' is not a recognized part of the sarcomere structure: In cell biology, there is no component known as the 'U zone' within the sarcomere.
Conclude that the 'U zone' is the correct answer as it is not a structure of the sarcomere, unlike the A band, H zone, and Z line which are well-defined parts of the sarcomere.
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