18 Questions
What are the two regulatory proteins that regulate actin in a sarcomere?
Troponin and tropomyosin
Which proteins hold adjacent myosin together with supporting proteins in a sarcomere?
Actin
What is the main function of troponin in muscle contraction?
It binds to tropomyosin and can move it out of the way
Describe the arrangement of myosin and actin within a myofibril.
They are tightly packed and organized in a specific overlapping pattern
What happens to the sarcomere when muscle contracts?
It shortens
What causes muscle contraction at the microscopic level?
Depolarization of the muscle cell
What is the boundary of a sarcomere where actin attaches to adjoining sarcomeres?
Z-line
What is the space between myosin filaments that contains only actin?
I band (light band)
Which protein binds to actin and blocks the myosin binding sites on actin?
Tropomyosin
What is the dark band that stretches end to end of myosin, containing both actin and myosin filaments?
A band (dark band)
Which protein contains binding sites for actin and an ATPase site?
Myosin
What is the arrangement of overlapping contractile proteins, actin and myosin within a myofibril?
Sarcomere
What is the role of troponin in muscle contraction?
Troponin binds to calcium, releasing tropomyosin from actin.
Describe the process of myosin binding to actin during muscle contraction.
Myosin heads grab onto actin, forming a crossbridge.
What happens when calcium is released in muscle cells?
Calcium binds to troponin, leading to the release of tropomyosin from actin.
What is the function of tropomyosin in muscle contraction?
Tropomyosin covers the myosin binding sites on actin.
Why is ATP required in muscle contraction?
ATP is needed for the power stroke of myosin, cross bridging release, and myosin detachment from actin.
How does the sarcoplasmic reticulum contribute to muscle contraction?
It stores and releases calcium for muscle cell contraction.
Test your knowledge on the structure of sarcomeres and the contractile proteins myosin and actin. Learn about the regulatory proteins troponin and tropomyosin and how they function within a sarcomere.
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