Rigor mortis is the stiffening of a body after death that occurs ...

Question

Rigor mortis is the stiffening of a body after death that occurs when myosin binds to actin but cannot unbind. What prevents myosin from unbinding?

Accepted Answer

Welcome back. Let's look at our next problem here. It says, when does rigor mortis start to develop? Well rigor mortis has that stiffness, the contraction of muscles after death where they remain contracted. So when we think about muscle contraction, I'm just gonna put up a quick diagram here of what's going on in the contracted state. So here is when the myosin protein has just bound to the act in fiber forming that cross bridge that causes the muscle to contract. You can see the mice in bound to the active. This yellow molecule here would be I'd realized a teepee was hydrolyzed to allow the myosin to bind. So it's A D. P. Plus a phosphate that's been hydrolyzed in order for the muscle to relax, the ADP and phosphate have to be released. And another molecule of A. T. P. Must come in and bind to that site. When that molecule of A. T. P. Binds and then is hydrolyzed by the myosin, the myosin will let go breaking the cross bridge and relaxing the muscle. So in order for the muscle to relax, you need a molecule of a TP to come in So after death when cellular respiration shuts down, there's no more a TP. This medicine is going to remain bound to the act in those cross bridges remaining formed and therefore the muscles remain in a contracted state. Even if the tendency was to relax. So when we look at our answer choices. We see that choice A. Says when A T. P runs out and that indeed is going to be the cause of rigor mortis because you need that molecule of a TP to allow the maya center release from the acting filament. So we'll just look through our other inter choices to understand why they're not correct. Choice B says when troponin binds to calcium. Well the troponin is on the diagram here, you can see the purple is a little calcium iron there and the binding of calcium troponin happens prior to muscle contraction. So before muscle contraction, this trope armisen is going to be blocking the myosin binding site on the act in calcium binds to troponin. That causes the truth commission to swing out of the way exposing the acting binding site and allowing the cross bridge to form. So the binding of troponin calcium occurs prior to muscle contraction is not the cause of rigor mortis. So, Choice B. Is not correct. Choice C. Says when the mice and head binds the exposed acting filament again, that initial binding of mice interact in the formation of the cross bridge is the beginning of the muscle contraction. So not going to be the result, the cause of this rigor mortis. This permanently contracted state. Choice C. Is not correct. And finally, Choice D when trouble missin wraps around the act in Well that when trouble mrs up here around the act and that blocks the binding of my son and prevents muscle contraction. So since rigor mortis is a permanent state of muscle contraction? That's not a correct answer. So again, when does rigor mortis start to develop? Choice A When a T. P runs out, see you in the next video?

Rigor mortis is the stiffening of a body after death that occurs when myosin binds to actin but cannot unbind. What prevents myosin from unbinding?

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