Multiple Choice
When calcium binds to troponin, what happens to tropomyosin?
15. Cytoskeleton and Cell Movement
Muscle Contractions
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Which of the following structures is composed of actin, but no myosin?
A
A band
B
M line
C
I band
D
Z line
Verified step by step guidance1
Understand the structure of a sarcomere, which is the basic unit of a muscle's striated muscle tissue. It is composed of repeating units between two Z lines.
Identify the components of a sarcomere: the A band, I band, H zone, M line, and Z line. Each of these has distinct characteristics and protein compositions.
Recall that actin and myosin are the primary proteins involved in muscle contraction. Actin is a thin filament, while myosin is a thick filament.
The I band is the region of the sarcomere that contains only thin filaments, which are primarily composed of actin. It does not contain myosin.
The A band contains both actin and myosin filaments, the M line is the center of the A band where myosin filaments are anchored, and the Z line is where actin filaments are anchored. Therefore, the I band is the structure composed of actin but no myosin.
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