Water soluble molecules I believe I may have misunderstood water solubility this entire time. I assumed that water soluble meant that it would literally dissolve in water. It would break down into atoms. A sugar molecule would break its bonds and become something else... However I must be mistaken because I'm reading about why DNA is spiral shaped and it says that it is to keep the hydrophobic bases inside the spiral to protect them from the water, but keeping the hydrophilic phosphate and sugar molecules on the outside. I would assume that because these molecules are hydrophilic they would disassociate from each other but this has to be incorrect. What am I misunderstanding about water solubility and what would happen if the bases were exposed to water?

This question would be more on-topic at Chemistry.SE, but I'll give you a quick answer. A substance is soluble in water when its solid form (such as a sugar cube) completely dissolves in water to become a sugar solution. The sugar molecules themselves are unaffected, essentially - instead of all being bound to one another in a crystal, they are now floating around in the water, hydrogen-bonded to the water molecules. The proof is in the taste - solid sugar and sugar solutions taste pretty much the same. If the sugar had been broken down into component hydrogen, oxygen, and carbon, it would taste _much_ different!

On the other hand, hydrolysis is what happens when water actually participates in a chemical reaction to break one or more molecular bonds within a certain molecule, breaking it down to two new molecules (or one molecule and an atom, or whatever). While sugar can be hydrolyzed, it requires either very high heat, or the presence of a catalyst such as an enzyme.