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Muscle Contraction - ADP and P i This in turn causes a...

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Muscle Contraction Muscle contraction events describing  the sliding-filament concept are listed  as follows. class="numbered">   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 
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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 
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Unformatted text preview: ADP and P 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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Muscle Contraction - ADP and P i This in turn causes a...

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