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Muscle Contraction

Muscle Contraction - i This in turn causes a change in the...

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Muscle Contraction Muscle contraction events describing the sliding-filament concept are listed as follows.   ATP binds to a myosin head and forms ADP + P i . When ATP binds to a myosin head, it is  converted to ADP and P i , which remain attached to the myosin head.    Ca 2+  exposes the binding sites on the actin filaments. Ca 2+  binds to the troponin molecule,  causing tropomyosin to expose positions on the actin filament for the attachment of myosin heads.    When attachment sites on the actin are exposed, the myosin heads bind to actin to form cross  bridges.   ADP and P i  are released, and a sliding motion of actin results. The attachment of cross bridges  between myosin and actin causes the release of ADP and P
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Unformatted text preview: i . This, in turn, causes a change in the shape of the myosin head, which generates a sliding movement of the actin toward the center of the sacromere. This pulls the two Z discs together, effectively contracting the muscle fiber to produce a power stroke. ATP causes the cross bridges to unbind. When a new ATP molecule attaches to the myosin head, the cross bridge between the actin and myosin breaks, returning the myosin head to its unattached position. Without the addition of a new ATP molecule, the cross bridges remain attached to the actin filaments. This is why corpses become stiff with rigor mortis (new ATP molecules are unavailable)....
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