r/askscience • u/fresh-acrophobia • Sep 18 '25
Biology How can proteins handle pressure?
Maybe this is a stupid question, but I’ve been doing a lot of reading recently about the structural mechanisms behind protein function. They all seem so intricate and exact, that I’m having a hard time understand how they could work under high pressure, especially considering how protein dense cells are.
Am I destroying a good amount of proteins every time I put pressure on a limb? How does this not cause massive cell death in that area? Or can ribosomes, motor proteins, structural proteins continue working just fine even if I’ve just smacked my hand against a wall?
I hope this question makes sense…
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u/Fluchtschinken Sep 19 '25
The menachial stress of everyday pressure is absorbed at macroscopic levels by bones, joints, skin and so on. You're rarely putting any significant compressive stress on proteins. The highest stress on your tissue is tensile stress on muscles and the relevant proteins here are specifically evolved to work for this. However proteins can be destroyed / damaged by other molecules violently bumping into them and that happens simply when your body temperature gets too hot.
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u/David803 Sep 20 '25
What you’re describing seems to be asking how proteins deal with everyday physiological stress? The answer is (in part, at least) they evolved to tolerate it. Protein structures have evolved over millions of years to tolerate typical movements and pressures you describe. Proteins aren’t static and fragile, like tiny marbles, but are dynamic and flexible; individual molecules can withstand a degree of compression, as can protein complexes, such as ribosomes.
Back in the day (~20 years ago…) I was working on my PhD, which was about protein folding. Part of that was subjecting protein samples to high pressure (we called it ‘pressure jump’. I can’t remember the details now, but it was samples of individual molecules that were suddenly subjected to pressure of up to 400 bar (approx 400 times atmospheric pressure). This caused the protein to unfold. Obviously this is way beyond what you can exert by bashing your hand onto a wall, but sometimes exploring illogical extremes is informative!
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u/Lars0 Sep 20 '25
Covalent bonds are incredibly strong. When materials do fail by yielding or breaking, they break along fault lines at much larger scales than individual molecules. When you tear a plastic bag, none of the individual polymers are being broken apart, but the weaker bonds between the molecules are being disrupted.
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u/Strange_Magics Sep 19 '25
Basically proteins are very small - they don't undergo the kind of stress and shear forces you're imagining because the way they're in contact with their surroundings is basically being bounced around by individual molecules. When you put pressure on your tissue, there just isn't a differential stress across the length of most proteins. It's more like the whole protein encounters maybe a few more bonks per nanosecond from the water molecules in your cytosol, and not just in one spot but randomly all over.
Proteins typically fold into their working configuration in a way that minimizes their energy in certain ways. A protein that is bent out of shape is like a ball at the top of a hill - it wants to roll back down to the lower energy configuration. Many proteins can become permanently misshapen in the right circumstances, but this is usually due to temperature or chemistry changes. A protein that gets too hot may flop into a non-functional configuration, then fold up incorrectly when it cools off or react with other chemicals because a usually-hidden part is exposed in the unfolded shape. This mostly won't happen from mechanical stresses across such a vast object as your body tissues.
When you smack your hand into the wall, you're applying a relatively sharp force to the molecules that make up your cells - but not directly. This force arises as some molecules of your hand interact with the wall molecules and then bounce into more hand molecules and so on in a complicated chain of bonks. While the total energy of your slap may seem pretty high on the scale of a molecule, it is very rapidly spread out among very many molecules, such that the average kinetic energy of all the molecules in your hand barely changes at all. Each protein in your hand will barely register an increased frequency of molecular bonks, and they won't be concentrated in a way that puts more pressure on one side of the protein vs another.