You may wonder how things get around inside cells if they are so crowded. It turns out that molecules move unimaginably quickly due to thermal motion. A small molecule such as glucose is cruising around a cell at about 250 miles per hour, while a large protein molecule is moving at 20 miles per hour. Note that these are actual speeds inside the cell.
Because cells are so crowded, molecules can’t get very far without colliding with something. In fact, a molecule will collide with something billions of times a second and bounce off in a different direction. Because of this, molecules are doing a random walk through the cell and diffusing all around. A small molecule can get from one side of a cell to the other in 1/5 of a second.
As a result of all this random motion, a typical enzyme can collide with something to react with 500,000 times every second.
In addition, a typical protein is tumbling around, a million times per second. Imagine proteins crammed together, each rotating at 60 million RPM, with molecules slamming into them billions of times a second. This is what’s going on inside a cell.
The motor proteins move cargo through the cell if diffusion isn’t fast enough to get things to their destination, which is especially important in extremely long cells such as neurons. Kinesin motors also help separate cells that are dividing.
It’s remarkable enough that cells contain these mechanical walkers, but I recently learned that they aren’t plodding along, but actually sprint at 100 steps per second. Cells are powered by electric motors spinning at 40,000 rpm.
Mitochondria also provide a fascinating look at just how fast things are inside cells. You may know that mitochondria are the power plants of cells; they take in food molecules, process it through the famous citric acid cycle, and then use oxygen to extract more energy, which is provided to the rest of the cell through molecules of ATP, the cell’s “energy currency”.
Mitochondria have many strange features - such as their own DNA separate from the cell’s - but one of their strangest features is they use electric motors to produce ATP. Mitochondria use the energy from oxidizing food to pump protons out of the cell, creating a voltage of 170mV across the cell. This voltage causes a complex enzyme to spin, and the mechanical energy of this spinning enzyme creates the ATP molecules that energize the rest of the cell.
src - https://www.righto.com/2011/07/cells-are-very-fast-and-crowded-places.html (ref) ref - https://jsomers.net/i-should-have-loved-biology/
origin - https://www.pipiscrew.com/?p=19391 cells-are-very-fast-and-crowded-places