Myosin strands have small heads that literally crawl

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Unformatted text preview: tropomysin and troponin proteins. • Myosin strands have small “heads” that literally crawl along the actin strands. This is the basis of muscle contraction. • Each movement of the myosin “head” requires one ATP, which is why muscles use up a lot of the body’s ATP. • This function of muscular movement requires the input of calcium ions. • Two types of muscle fibers: • Slow-twitch: Slow to contract. Contain abundant mitochondria, and store myoglobin (an oxygen-storing protein similar to hemoglobin), which make these fibers dark. They are useful for endurance activities, such as long-distance running. “Dark meat” on a turkey. • Fast-twitch: Contract quickly. These have fewer mitochondria and less blood supply...
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