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I'm familiar with the cross bridge cycle and how the sarcomere contracts, but I have two related questions. I’ve read that when the myosin head cocks, it’s similar to a spring-loaded mousetrap. But is this actually true or just an analogy? In other words, is the chemical energy actually turned into elastic potential energy and then mechanical energy as the myosin head drives forward or am I misunderstanding this? And if this is correct, what is the evolutionary purpose for storing the energy as elastic potential energy? In other words, you could imagine a different configuration, where instead of the hydrolyzation of ATP to ADP + P being used to cock the myosin head into its high energy conformation, stored as elastic energy, and THEN driving the myosin head forward when the cycle is complete, you could envision a configuration where there is no intermediate step of storing the elastic energy. Instead the chemical energy is directly used to move the myosin heads and contract the sarcomere. So why does this intermediate step exist?

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  • $\begingroup$ At such immensely small sizes, concepts like elasticity drastically change. The ability to "stretch" a molecule is nothing at all like elasticity in larger structures. As soon myosin moves, the rest of it moves virtually instantly. $\endgroup$ – forest Dec 30 '17 at 7:07

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