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Comment by kens | Hacker News Reader

Yes, cells are extremely crowded and fast-moving inside. Molecules are moving at 250 miles per hour inside cells due to thermal motion, and a particular molecule collides with other molecules billions of times per second.

When you see an animation of a cell, it's puzzling how the right molecule shows up in the right place. But in reality, a typical enzyme collides with something to react with 500,000 times per second just from random motion.

I wrote a blog post discussing this in more detail: http://www.righto.com/2011/07/cells-are-very-fast-and-crowde...

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>it's puzzling how the right molecule shows up in the right place.

Most chemistry is like that though isn't it? Everything is flying around randomly but the electron density distributions mean some "bonds" have better probability of being broken and made during reactions.

It is almost like life is possible just due to a biological fuzzer.

I'm trying to visualize that in my mind. But what is BETWEEN the molecules? Vacuum?

Isn’t it Cytoplasm? https://en.m.wikipedia.org/wiki/Cytoplasm

Imagine a glass of water and all the water molecules in it. They are all touching (kind of) and constantly moving around. There is a bit of space between the molecules, the inter-molecular space, which is a vacuum. Keep in mind that the molecules aren't really touching since they aren't built from rigid spheres but have electron clouds. The water molecules repel each other if they get too close, but also attract each other via hydrogen bonds, so they are about 0.3 nm apart. (Compare to 3 nm semiconductor process node.)

A cell is similar (since it is 60% water), but with many other types of molecules as well.

Thanks for the explanation. I guess the reason I find it hard to visualize is that we ordinarily think that 'vacuum sucks". If there is container which has been pumped empty of air and we make a hole in it it sucks in air. So it looks like empty/vacuum space "sucks" anything around in it.

But that is obviously a misconception. Vacuum is not attracting anything, it is the fast moving molecules around it that PUSH themselves into the vacuum if we make a whole in the container.

What makes it hard to visualize is that we don't see the fast-moving molecules ever, which are forcing themselves into the container through the pierced hole by the power of their own (tiny) momentum yet very fast speed. :-)

It is also counter-intuitive that tiny things could have fast speeds, perhaps because we think in terms of a person being able to walk much faster than say an ant.

There is also water between the molecules, but note that cells are generally quite crowded places. You can check out David Goodsell's images for getting a sense of how crowded a cell is.

https://www.google.com/search?q=David+Goodsell&tbm=isch

Interesting comment / blogpost! Thanks, learned some new things today :)

I was baffled in school how tRNA "moves" amino acid to ribosome. Asked and got no answer.

Found out much later — tag so many amino acids, that it would stumble on ribosome. Genius.

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