This is because iron is used to make a protein called hemoglobin. This protein helps blood cells carry oxygen around the body.
Answer:
<u>Once the myosin-binding sites are exposed, and if sufficient ATP is present, myosin binds to actin to begin cross-bridge cycling. Then the sarcomere shortens and the muscle contracts. In the absence of calcium, this binding does not occur, so the presence of free calcium is an important regulator of muscle contraction.</u>
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