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Answer:
C. Kinesin hydrolyzes ATP.
Explanation:
The central force-generating element that the two types of motor proteins (Kinesin and Myosin) have in common includes the site of ATP binding and the machinery necessary to translate ATP hydrolysis into an allosteric conformational change. Kinesin must use the energy derived from ATP binding and hydrolysis to force a large movement in part of the protein molecule. When kinesin forms a rigor-like tight association with the head location of the microtubule, the ATP is bound to the kinesin, and it is hydrolysis of ATP that promotes release of the motor from its track. Thus, myosins can typically drive filament sliding much more rapidly than kinesins, even though they hydrolyze ATP at comparable rates and take molecular steps of comparable length.
Answer:
The order of events would be:
4.Threshold stimulus, Na+ channels open. This is the first event
5.Na+ influx, Depolarization. Second event
2.Na+ channels close, K+ channels open. This is the third event
1.K+ efflux, Repolarization. Fourth event
3.Hyperpolarization, K+ channels close
Explanation:
In resting state, the membrane is negative inside, and K+ concentration is higher than outside. Na+ concentration is higher outside instead.
Sodium influx is responsible for membrane depolarization. It's the event to produce the action potential. When sodium channels are closing, potassium channels open and K+ go outside until repolarization occurs. But now we have both ions in different sides of the membrane, and this can't be stimulated again to produce other action potential. The membrane will remain refractory to respond to the adequate stimulus until ions migrate to their original sites. This is Na+ outside, and K+ inside. This is responsibility of the Na+/ K+ pump, that uses ATP to pump Na+ out, and K+ in. Once both ions had been relocated in the membrane, this is ready to receive a correct stimulus to produce a new action potential.
