Osmosis!

As in Osmosis Jones :) No, no. Osmosis is the net movement of a solvent through a partially permeable membrane from an area of high concentration to an area of low concentration. Not to be confused with diffusion, which is just a net movement of molecules from a high concentration to a low concentration. The overall goal with both osmosis and diffusion is to equalize the concentration both inside and outside, say, a cell.

There are three states that a solution can be in:
1. Isotonic - Equal concentrations both inside and outside of the cell
2. Hypertonic - More solute in the cell than solvent (more water outside the cell, more molecule inside)
3. Hypotonic - More solvent in the cell than solute (the opposite of above)

I think that's right? Sorry, it's been a really long time since I've had to look at this stuff.

My favorite example of osmosis is explaining why, if you are stranded at sea, you should not drink the salt water. Sure it tastes good and temptation is hard to resist when you are baking in the sun, but you will kill yourself much, much quicker. This is because of the high concentration of salt in the sea water compared to the water in your body. Once you have a high concentration of salt water in your body (creating a hypotonic environment), the fresh water will rush out of your cell in hopes to equalize the concentration! Which will not happen because there is not enough fresh water in your body at that point. You will die.

But at least now you know WHY.

Source: http://www.movieposterdb.com/poster/b59084de

Answer to yesterday's question: A nucleotide is a base (either A, T, G, or C), a sugar (either deoxyribose or ribose), and a phosphate group. A nucleoside is just a base and a sugar.

What famous experiments can you find demonstrating osmosis? I'm sure all of you performed this in your high school biology class!