Answer:
When a muscle cell contracts, the myosin heads each produce a single power stroke.
Explanation:
In rest, attraction strengths between myosin and actin filaments are inhibited by the tropomyosin. When the muscle fiber membrane depolarizes, the action potential caused by this depolarization enters the t-tubules depolarizing the inner portion of the muscle fiber. This activates calcium channels in the T tubules membrane and releases calcium into the sarcolemma. At this point, <em>tropomyosin is obstructing binding sites for myosin on the thin filament</em>. When calcium binds to the troponin C, the troponin T alters the tropomyosin by moving it and then unblocks the binding sites. Myosin heads bind to the uncovered actin-binding sites forming cross-bridges, and while doing it ATP is transformed into ADP and inorganic phosphate which is liberated. Myofilaments slide impulsed by chemical energy collected in myosin heads, <u>producing a power stroke</u>. The power stroke initiates when the myosin cross-bridge binds to actin. As they slide, ADP molecules are released. A new ATP links to myosin heads and breaks the bindings to the actin filament. Then ATP splits into ADP and phosphate, and the energy produced is accumulated in the myosin heads, which starts a new binding cycle to actin. Z-bands are then pulled toward each other, thus shortening the sarcomere and the I-band, and producing muscle fiber contraction.
Two adaptations of a saguaro cactus in order to store water are as following:
1. large stems can store water.
2.thick waxy skin in order to reduce water loss through pores.
I believe that the youth movement originated with the baby boomers, the huge generation born after the world war II. By 1970, 58.2 % of the population in America was under the age of 35 years. The economic boom of the 1950s meant more families could afford to send their children to College. College life gave the young people a sense of freedom and independence. It was on college campuses across the nation that youth protest movements began and reached their peak.
Answer:
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Explanation:
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<span>If they have a nucleus, they are eukaryotic</span>