How did data on sarcomere structure inspire the sliding-filament model of muscle contraction? Explain why the observation that muscle cells contain many mitochondria and extensive smooth endoplasmic reticulum turned out to be logical once the molecular mechanism of muscular contraction was understood.

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Accepted Answer

Hi everyone. Let's look at our next question here. It says, why do muscle cells need to have many mitochondria? Well let's think about what mitochondria do and what muscle cells do mitochondria obviously are in the business of producing energy. Specifically a TP. And it's obviously common sense to think muscle cells need energy to move but let's be specific about it. So why do muscle cells need a teepee specifically? Well, the Maya sin in muscle cells needs a T. P. To bind to the act in filming to cause a muscle contraction. So eight EP comes in binds to the miocene protein as hydrolyzed to A V. P. Plus phosphate. That allows it to move down and bind to the acting, forming that cross bridge. And it also needs a T. P. To release from the acting to relax the muscle. So once it's bound in that cross bridge that same binding site, the ADP and phosphate are released that were hydrolyzed. Allowed to bind another molecule of ADP needs to bind that site to allow the medicine to release its hydrolyzed in that process. So it needs a T. P. Both to contract and to relax. And in addition in order for my son to bind, you have to have uh trope a missin oops move away from the Mayas and binding site. Commission blocks that binding site on the acting filament in order for it to move away, A calcium ion has to bind to the troponin. The troponin moves the trip causes the trip mission to move out of the way. Well all that calcium they need your pumping calcium in interior where you already have calcium ions that needs active transport. So active transport of the calcium needs A. T. P. To take place. So the A. T. P. Is needed for the mason both to contract and relax the muscles and A. T. P. Is needed for active transport of calcium to bind the troponin and get out of the way and allow the medicine binding. So that's a lot of 80 P. Needs and therefore they need many mitochondria. So let's look at our answer choices and see what's correct choice A. Says to ensure that various molecules are transported to where they are needed. Well we do have a need for calcium to be transported. Um But this is how why do they need so many mitochondria? So this doesn't seem like a very complete answers. Let's put a little dot. Um Not going to rule it out right away but see if there's a better answer. Further on choice B. Says to protect the muscle cells from desiccation drying out. Well that's not correct. Not the role of A. T. P. Enjoy C. To provide sufficient energy for muscle movement. So this is a better answer than a. Because obviously the greatest need is for that A TP to allow the contraction and relaxation of muscle um that the miocene needs in addition to transport the calcium that allows that. But um transport the calcium is just a small part of this. So a better answer, Choice C to provide sufficient energy for muscle movements. And, finally, Choice D. Says to ensure that enough oxygen is provided. No, that's not what we're looking for specifically. Why do they need many mitochondria is to have their A. T. P. Needs met? So again, why do muscle cells need to have many mitochondria? Choice C. To produce sufficient energy for muscle movements? See you in the next video.

Verified Solution

Key Concepts

Sarcomere Structure

Sliding-Filament Model

Mitochondria and Smooth Endoplasmic Reticulum in Muscle Cells