What is the basic mechanism of contraction at the level of myofilaments?

Video transcript

Hey, everyone. Let's take a look at this question together which of the following happens during the resting state of the muscle contraction cycle. Is it answer choice. A calcium ions bind to troponin. Answer choice. Batp is hydrolyzed to ad P answer choice C Tropomyosin blocks the active sites on acting or answer choice. Datp molecules binds to the Myosin head. Let's work this problem out together to try to figure out which of the following answer choices best explains what happens during the resting state of the muscle contraction cycle. So in order to solve this question, we have to recall what we have learned about the muscle contraction cycle and what occurs during the resting state. And we can recall that in the resting state of muscle contraction, the formation of the Myosin cross bridges are blocked. And what we mean by the Myosin cross bridge formation is blocked is that Tropomyosin covers the act in binding site which prevents the formation of the cross bridge. So during the resting state of the muscle contraction cycle, the formation of the cross bridges is blocked because Tropomyosin binds to the active sites on active, which is answer choice C the correct answer and all other answer choices are incorrect. Since answer choice A which says calcium ions bind to troponin is incorrect. Since the bind of calcium ions to troponin occurs in the activation phase. Answer choice B which says A TP is hydrolyzed to AD P is incorrect. Since the hydro organization of A TP into AD P is part of the energy dependent steps during the contraction cycle but occurs after the resting state when the muscle is activated. And lastly answer choice D which says A TP molecules bind to the myosin head is incorrect. Since the binding of the A TP molecules to the myosin head occurs during the later stages of the contraction cycle. When the myosin head is preparing for the formation of another cross bridge. And answer choice C is the only correct answer choice. I hope you found this video to be helpful. Thank you and goodbye.