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(15). Muscle cells contain , which are composed of thin filaments made of ts made ofarranged as thousands of . Myosin is a mo
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Muscle cells contain 'myofibrils' which are made of thin filaments made of 'actin' and thick filaments are made of 'myosin' arranged as thousands of 'sarcomeres'. Myosin is a motor protein that moves towards the 'tropomyosin' end of actin. Calcium is stored in specialized endoplasmic reticulum called 'sarcoplasmic reticulum' and released in response to the depolarization of 'sarcolemma'. Calcium binds to 'Troponin c' which results in a confirmational change in Troponin uncovering the myosin binding sites on actin. Binding of ATP to myosin causes the 'binding' of myosin from actin. The hydrolysis of ATP to ADP and Pi causes a confirmational change in myosin, moving the head of myosin, ~5mm along the actin filament. The power stroke is initiated by the release of Pi and during the power stroke ADP also is released. At the end of the cycle, myosin is 'released from' actin.

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