This post or something similar has been posted to HN before: http://www.righto.com/2011/07/cells-are-very-fast-and-crowded-places.html?m=1 http://www.righto.com

This post or something similar has been posted to HN before: http://www.righto.com/2011/07/cells-are-very-fast-and-crowded-places.html?m=1 http://www.righto.com/2011/07/cells-are-very-fast-and-crowde... It makes a lot more sense when described from this perspective: >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, not scaled-up speeds. I'm not talking about driving through a crowded Times Square at 20 miles per hour; to scale this would be more like driving through Times Square at 20 million miles per hour! >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. Watching the video, you might wonder how the different pieces just happen to move to the right place. In reality, they are covering so much ground in the cell so fast that they will be in the "right place" very frequently just by chance.