How is ATP used to create mechanical work in muscle cells?

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How is ATP used to create mechanical work in muscle cells?

#1  Postby Jbags » Aug 04, 2020 7:51 am

I've spent some time reading up on this, but none of the explanations I have found online seem to answer this problem sufficiently (or in a way that I can understand), so turning to the enlightened minds on this forum for guidance.

To explain in more detail, I understand that:

a. ATP the sole source of energy used in cells (though there are many ways cells can generate ATP)
b. The energy in question is chemical energy, stored in the phosphate bonds of ATP.
c. ATPase enzymes break the phosphate bonds, chemical energy is released
d. The release of this chemical energy changes the shape and binding of protein filaments to create mechanical work

What I don't understand is point d. - how does this release of chemical energy lead to mechanical work? Why do the proteins change shape, and why does this lead to a force being exerted?

The section on 'crossbridge cycling' on this wikipedia page seems to be relevant, but crucially in this sentence "The myosin head then releases the inorganic phosphate and initiates a power stroke, which generates a force of 2 pN", why is the power stroke initiated? Why is a directional force generated?
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Re: How is ATP used to create mechanical work in muscle cells?

#2  Postby Cito di Pense » Aug 04, 2020 8:32 am

Because the atoms in molecules exert forces on each other; when the configuration changes, the forces change. Don't get lost in terminology. Stick to the basics, if that's all you can understand. You can even consider that work and energy are not really different in some philosophical way. Energy converts to work (speeding up of a car, but the work is the expansion of the gases in the cylinder on ignition). This is merely fundamental thermodynamics, and you should try to understand that before you tackle biochemistry and biophysics.

Jbags wrote:none of the explanations I have found online seem to answer this problem sufficiently (or in a way that I can understand)


"Suffiiciently" is a bit subjective. How long are you willing to study and how do you plan to test your knowledge (or anyone else's that you come across)? You haven't said how you could be satisfied by any answers you receive. This is elementary for anyone who's studied second-year physical chemistry, which is not the endpoint of a chem degree. Nobody can just pour this knowledge into your head. What I've found about a lot of wikipedia articles is that they can stimulate your curiostity, but cannot even begin to satisfy it in the article that starts it off. A wikipedia article is not the beginning of any account, not with stuff like this.

Jbags wrote:
The section on 'crossbridge cycling' on this wikipedia page seems to be relevant, but crucially in this sentence "The myosin head then releases the inorganic phosphate and initiates a power stroke, which generates a force of 2 pN", why is the power stroke initiated? Why is a directional force generated?


That's specialist biophysics. You should expect to study awhile before you "understand" it. At some point, even before this, the wikipedia loses its capacity to educate the novice. Don't rely on it for deep insight when it goes this far. "Power stroke" is metaphorical in the account of myosin function - the term comes from the design of heat engines. Why is directional force generated? If it wasn't, it wouidn't work, would it? It's the underlying structure that leads to the direction. Why ask why?
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Re: How is ATP used to create mechanical work in muscle cells?

#3  Postby newolder » Aug 04, 2020 9:42 am

Brief aside:
Cito di Pense wrote:... Nobody can just pour this knowledge into your head. ...


ATP is Advanced Teaching Practice?



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Re: How is ATP used to create mechanical work in muscle cells?

#4  Postby aban57 » Aug 04, 2020 10:45 am

Cito di Pense wrote:Because the atoms in molecules exert forces on each other; when the configuration changes, the forces change. Don't get lost in terminology. Stick to the basics, if that's all you can understand. You can even consider that work and energy are not really different in some philosophical way. Energy converts to work (speeding up of a car, but the work is the expansion of the gases in the cylinder on ignition). This is merely fundamental thermodynamics, and you should try to understand that before you tackle biochemistry and biophysics.

Jbags wrote:none of the explanations I have found online seem to answer this problem sufficiently (or in a way that I can understand)


"Suffiiciently" is a bit subjective. How long are you willing to study and how do you plan to test your knowledge (or anyone else's that you come across)? You haven't said how you could be satisfied by any answers you receive. This is elementary for anyone who's studied second-year physical chemistry, which is not the endpoint of a chem degree. Nobody can just pour this knowledge into your head. What I've found about a lot of wikipedia articles is that they can stimulate your curiostity, but cannot even begin to satisfy it in the article that starts it off. A wikipedia article is not the beginning of any account, not with stuff like this.

Jbags wrote:
The section on 'crossbridge cycling' on this wikipedia page seems to be relevant, but crucially in this sentence "The myosin head then releases the inorganic phosphate and initiates a power stroke, which generates a force of 2 pN", why is the power stroke initiated? Why is a directional force generated?


That's specialist biophysics. You should expect to study awhile before you "understand" it. At some point, even before this, the wikipedia loses its capacity to educate the novice. Don't rely on it for deep insight when it goes this far. "Power stroke" is metaphorical in the account of myosin function - the term comes from the design of heat engines. Why is directional force generated? If it wasn't, it wouidn't work, would it? It's the underlying structure that leads to the direction. Why ask why?



Still your condescending self, are you ?

It's kind of reassuring, in these times of utter chaos out there, that we can find some sense of continuity and normalcy here.
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Re: How is ATP used to create mechanical work in muscle cells?

#5  Postby campermon » Aug 04, 2020 10:50 am

Jbags wrote:

What I don't understand is point d. - how does this release of chemical energy lead to mechanical work? ...


Work / energy / heat are the same thing. A good place to start is here; https://en.wikipedia.org/wiki/Work_(thermodynamics)

:thumbup:
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Re: How is ATP used to create mechanical work in muscle cells?

#6  Postby Jbags » Aug 05, 2020 4:46 am

Cito di Pense wrote:Why is directional force generated? If it wasn't, it wouidn't work, would it? It's the underlying structure that leads to the direction. Why ask why?


Well isn't that a great attitude for a forum dedicated to rational inquiry. Let's just not ask why, because what's the point in knowledge anyway.

Cito di Pense wrote:Nobody can just pour this knowledge into your head.


No, indeed, in my experience it comes from asking questions and discussing the answers.

campermon wrote:
Jbags wrote:

What I don't understand is point d. - how does this release of chemical energy lead to mechanical work? ...


Work / energy / heat are the same thing. A good place to start is here; https://en.wikipedia.org/wiki/Work_(thermodynamics)

:thumbup:


Thanks for this. Actually, this points to an example I understand of how chemical energy leads to mechanical work.

> Combustion of hydrocarbons leads to chemical energy stored on molecular bonds being released as thermal energy.
> The thermal energy heats up gases confined in a contained space (cylinder) increasing pressure in all directions
> The cylinder is designed in a way that it can only expand in one direction - by movement of a piston head - so movement occurs in a specific direction.

There are only a few simple causal links required to get from start to finish - molecular bond breaks releasing thermal energy, hot gases expand, expansion of gas is funneled in a specific direction.

I can't create the similar causal chain for the use of ATP in muscles. As far as I can tell, it is not the same as combustion - pressure is not generated by heating a medium up and then funneling increased pressure in a specific direction.

Rather, the 'shape' of the myosin molecule changes in a specific direction - but why is that? Is the myosin molecule like a rubber band, that's stretched by the binding of ATP and released by the breaking of these bonds? If so, why does it 'snap back' to a previous shape?

--

For the record - I appreciate anyone willing to help me on my journey to understanding; even if I still have a way to go, every little helps.
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Re: How is ATP used to create mechanical work in muscle cells?

#7  Postby Cito di Pense » Aug 05, 2020 5:47 am

Jbags wrote:
No, indeed, in my experience it comes from asking questions and discussing the answers.


Go ahead and ask. Have fun.

Jbags wrote:Thanks for this. Actually, this points to an example I understand of how chemical energy leads to mechanical work.


It's something I pointed out in my initial reply to you. You asked, and I answered, but apparently, it wasn't fun enough. Coiled springs can store and release energy, too, but that also isn't exactly how muscle tissue works. You're going to rely on metaphor.
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Re: How is ATP used to create mechanical work in muscle cells?

#8  Postby Ironclad » Aug 05, 2020 6:44 am

Low-brow though it may be, some sports websites dedicate themselves to understanding such chemistry. Perhaps to help sell product, perhaps to be seen as less caveman. I used to take ATP as a supplement myself, while it allowed for a small noticeable uplift in stamina it also left me looking puffy.
Have a read of this, there’s not much there but you might find something of use..

https://www.bodybuilding.com/content/at ... rtant.html
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Re: How is ATP used to create mechanical work in muscle cells?

#9  Postby Cito di Pense » Aug 05, 2020 7:10 am

Ironclad wrote:Low-brow though it may be, some sports websites dedicate themselves to understanding such chemistry. Perhaps to help sell product, perhaps to be seen as less caveman. I used to take ATP as a supplement myself, while it allowed for a small noticeable uplift in stamina it also left me looking puffy.
Have a read of this, there’s not much there but you might find something of use..

https://www.bodybuilding.com/content/at ... rtant.html


You can't "take ATP". You can take nutritional supplements purported to enhance ATP concentration. Purported. Studies have not shown conclusively that enhanced levels of ATP become bioavailable as a consequence, or else you'd want to point to one. Now we can spin out the whole noise about nutritional supplements and the studies that purportedly show (or question) their "effects". Sciency! Woooo!

I used to take ATP as a supplement myself, while it allowed for a small noticeable uplift in stamina it also left me looking puffy.


Know what this is called? It's called an anecdote. Right here, on a website devoted to rational inquiry. Advertised, anyway.
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Re: How is ATP used to create mechanical work in muscle cells?

#10  Postby Adco » Aug 05, 2020 10:11 am

https://www.amazon.com/Quantum-Evolutio ... B01CC8B96Q

This is a book I found interesting. Some of it deals with the chemistry that takes place in the body.
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Re: How is ATP used to create mechanical work in muscle cells?

#11  Postby Cito di Pense » Aug 05, 2020 10:24 am

Adco wrote:https://www.amazon.com/Quantum-Evolution-Multiverse-Johnjoe-McFadden-ebook/dp/B01CC8B96Q&tag=rationskepti-20

This is a book I found interesting. Some of it deals with the chemistry that takes place in the body.


That link up there is broken and something about RatSkep's engine fucks it up if you just post a raw link. Look at the trailing garbage with the ampersand and following.

Better?

Yep, it is. You should embed the link with tags. Oh, so much work. Not fun on a tablet, or touch interface in general.

This one looks to wave its hands at the word "quantum". To understand muscle function, that's overkill, and trying to sell a sexy word instead of understanding.

From the blurb-review:

He shows how living organisms have the ability to will themselves into action.


Fuck me. That's some dim fucking shit. If the book has some chemistry in it, you couldn't sell it to me that way.

From a more balanced review (on the amazon site):

When he finally does get to the point of the book, at the dry end of the book, what we realize is two things: (1) the author has carefully sculpted and constructed his overviews of the various systems within science to cherrypick and put forth the specific interpretations within these fields that agree with his final conclusions. So we're not getting so much an objective overview of each field as we are a very carefully constructed, almost lawyerly, argument meant to support a very subjective case. (2) The final arguments he makes about how he thinks life and consciousness may have arisen in the universe are incredibly specious, even granting that he admits its pure speculation.


This sounds exactly like where the blurb-review is pushing us.
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Re: How is ATP used to create mechanical work in muscle cells?

#12  Postby campermon » Aug 05, 2020 10:43 am

Jbags wrote:
Rather, the 'shape' of the myosin molecule changes in a specific direction - but why is that?


this is fairly accessible; https://www.ncbi.nlm.nih.gov/books/NBK21724/

:thumbup:
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Re: How is ATP used to create mechanical work in muscle cells?

#13  Postby felltoearth » Aug 05, 2020 12:41 pm

campermon wrote:
Jbags wrote:
Rather, the 'shape' of the myosin molecule changes in a specific direction - but why is that?


this is fairly accessible; https://www.ncbi.nlm.nih.gov/books/NBK21724/

:thumbup:

An amazing read Campermon. Thanks!
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Re: How is ATP used to create mechanical work in muscle cells?

#14  Postby campermon » Aug 05, 2020 1:04 pm

:cheers:
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Re: How is ATP used to create mechanical work in muscle cells?

#15  Postby campermon » Aug 05, 2020 1:20 pm

campermon wrote:
Jbags wrote:
Rather, the 'shape' of the myosin molecule changes in a specific direction - but why is that?


this is fairly accessible; https://www.ncbi.nlm.nih.gov/books/NBK21724/

:thumbup:


plus, nice little link here demonstrating how molecules change shape when electrons get moved about - essentially a chemically reaction is just the shifting about of electrons.

https://www.newscientist.com/article/22 ... electrons/
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Re: How is ATP used to create mechanical work in muscle cells?

#16  Postby Evolving » Aug 05, 2020 1:27 pm

Amazing how much it's possible to get done for 80p.
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Re: How is ATP used to create mechanical work in muscle cells?

#17  Postby campermon » Aug 05, 2020 1:32 pm

Evolving wrote:Amazing how much it's possible to get done for 80p.


iswydt

:lol: :lol: :lol: :lol: :lol: :lol:
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Re: How is ATP used to create mechanical work in muscle cells?

#18  Postby Jbags » Aug 06, 2020 4:02 am

Ironclad wrote:Low-brow though it may be, some sports websites dedicate themselves to understanding such chemistry. Perhaps to help sell product, perhaps to be seen as less caveman. I used to take ATP as a supplement myself, while it allowed for a small noticeable uplift in stamina it also left me looking puffy.
Have a read of this, there’s not much there but you might find something of use..

https://www.bodybuilding.com/content/at ... rtant.html


Thanks for the link, actually a pretty accessible write up! I've found some good reads on bodybuilding.com in the past that have helped with my own strength training. I have taken creatine supplements in the past for the same reason, but found the marginal gain not valuable enough for me as only an amateur. On a related note, I found examine a useful source for aggregating scientific evidence behind supplement & nutrition claims that erupt from all corners of the internet.
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Re: How is ATP used to create mechanical work in muscle cells?

#19  Postby Jbags » Aug 06, 2020 4:33 am

campermon wrote:
campermon wrote:
Jbags wrote:
Rather, the 'shape' of the myosin molecule changes in a specific direction - but why is that?


this is fairly accessible; https://www.ncbi.nlm.nih.gov/books/NBK21724/

:thumbup:


plus, nice little link here demonstrating how molecules change shape when electrons get moved about - essentially a chemically reaction is just the shifting about of electrons.

https://www.newscientist.com/article/22 ... electrons/


Thanks campermon for both of these links! Took a little while to make my way through them and piece things together, but I definitely feel like I've taken multiple steps forward.

I found the shape of myosin II particularly interesting, how the head has a large 'cleft' that opens / closes around an actin binding site, as ATP is bound -> hydrolysed -> released.

I feel like I'm nearly there now, to answer my previous question "why does it snap back to its original shape" the answer is electric potential energy - as described in the second link. The binding of ATP 'cocks' the system, similar to how you can cock the hammer of a pistol, storing energy in a spring. Binding to the actin filament, releases the phosphorus ion and ADP, and the myosin filament changes shape to return to its lowest energy state - just like a spring uncoiling.

In that way, the chemical energy stored in the ATP phosphorous bonds is transferred into electric potential energy in changing the shape of the myosin protein. I find this fascinating because it's actually a very different chain of events compared to combustion - where the overall story is the same (chemical energy is turned into a directional force) the actual path of getting from A to B is very different. Thanks again!

Sharing a couple of interesting things I found while doing more reading:

1) an animation of the Myosin II ATP hydrolysis cycle



2) a less related video, but one I found fascinating nonetheless, of an animation of DNA replication (animation at 3:40)

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Re: How is ATP used to create mechanical work in muscle cells?

#20  Postby Ironclad » Aug 06, 2020 3:33 pm

Cito di Pense wrote:
Ironclad wrote:Low-brow though it may be, some sports websites dedicate themselves to understanding such chemistry. Perhaps to help sell product, perhaps to be seen as less caveman. I used to take ATP as a supplement myself, while it allowed for a small noticeable uplift in stamina it also left me looking puffy.
Have a read of this, there’s not much there but you might find something of use..

https://www.bodybuilding.com/content/at ... rtant.html


You can't "take ATP". You can take nutritional supplements purported to enhance ATP concentration. Purported. Studies have not shown conclusively that enhanced levels of ATP become bioavailable as a consequence, or else you'd want to point to one. Now we can spin out the whole noise about nutritional supplements and the studies that purportedly show (or question) their "effects". Sciency! Woooo!

I used to take ATP as a supplement myself, while it allowed for a small noticeable uplift in stamina it also left me looking puffy.


Know what this is called? It's called an anecdote. Right here, on a website devoted to rational inquiry. Advertised, anyway.

I am pretty sure you know what I was meaning, Cito. You are naughty sometimes.
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