muscle contraction

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Ca2+ diffuses out of the sarcoplasmic reticulum. Ca2+ binds to troponin and tropomyosin causing them to change shape and move, exposing myosin head binding sites. This allows myosin to move and bind to the myosin head binding sites, and once bound they are able to bend and contract pulling it towards the centre of the muscle. When it bends it releases ADP. The myosin unbinds from the binding site, using ATP (ATP to ADP + Pi), and returns to its original position. This process of binding and unbinding repeats until muscle contraction is complete. Phosphocreatine is an example of a substance that assists with muscular contraction, it is involved in producing ATP for contraction to occur. Phosphocreatine + ADP ---> ATP + Creatine