What force makes muscles contract?

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Main Question or Discussion Point

I know muslces have fibers and all sorts of structures but how do they actually attract themselves to each other on a very atomic level? Is it some sort fo chemical bonding force or?
 

Answers and Replies

BillTre
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Its a complex process involving many changes in binding and changes in the shape of proteins that make up the fibers in the muscle cells.

Generally speaking, the binding of between two interacting proteins is not that strong. However, it would be repeated many many times in each muscle fiber where thousands or millions of interacting proteins would be involved. Binding sites are usually made by a mix of different weak interactions on the 3D surfaces of the two things being bound together. They usually don't involve covalent bonds, but may involve charge and other interactions.
The binding of two proteins may cause one or both proteins to change shape.
In addition to these general considerations on binding, ATP (cellular energy source) is involved in muscle contraction by driving certain changes in the protein shape. Shape changes such as this, in turn involve relatively weak interactions within the particular proteins, which drives their shape changes, which in turn causes muscle contraction.

It is usually triggered by an increase in Ca++ whihc binds to particular muscle proteins.

Muscles actively contract (shorten). They lengthen passively (no energy involved, no force generated, other muscles contraction causes them to lengthen).

Wikipedia has a extensive article in this. See the article for more details.


1008_Skeletal_Muscle_Contraction copy.jpg

Picture from here.
 
362
32
Its a complex process involving many changes in binding and changes in the shape of proteins that make up the fibers in the muscle cells.

Generally speaking, the binding of between two interacting proteins is not that strong. However, it would be repeated many many times in each muscle fiber where thousands or millions of interacting proteins would be involved. Binding sites are usually made by a mix of different weak interactions on the 3D surfaces of the two things being bound together. They usually don't involve covalent bonds, but may involve charge and other interactions.
The binding of two proteins may cause one or both proteins to change shape.
In addition to these general considerations on binding, ATP (cellular energy source) is involved in muscle contraction by driving certain changes in the protein shape. Shape changes such as this, in turn involve relatively weak interactions within the particular proteins, which drives their shape changes, which in turn causes muscle contraction.

It is usually triggered by an increase in Ca++ whihc binds to particular muscle proteins.

Muscles actively contract (shorten). They lengthen passively (no energy involved, no force generated, other muscles contraction causes them to lengthen).

Wikipedia has a extensive article in this. See the article for more details.

View attachment 253117
Picture from here.
Nice post, so would you say it would be something like an ionic bond contracting the muscles?
 
BillTre
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Something like an ionic bond (or maybe a weaker charge attraction) could be involved in some of the many aspects of the process (binding or attachment, shape changes).
Other attractive forces could also be involved like hydrophobic attraction.
There are so many different interactions going onin this complex process, that I hesitate to rule much out.
 
DaveC426913
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yes I have, the answers are too broad and not at the atomic level
I used to wonder the same thing. How does tissue actually contract.

When I saw it animated at the atomic level it brought a whole new visual element to it for me.

actin.gif


crossbridgecycle.gif
 
BillTre
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I would hesitate to say I know exactly what kinds of binds are forming and breaking at an atomic level.
Determining what the interactions are the atomic level would require protein crystalolgraphy of its more modern equivalents that produce the kind of detail.
The blobs in many molecular models (such as @DaveC426913 or I showed in earlier posts) will contain thousands of millions of atoms. Tens or hundreds of these atoms may be involved in these kinds of interactions.
 

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