Thermodynamics is a notoriously difficult subject for the undergraduate in medicine or biology (or physics, for that matter!). It is also tinged with notoriety due to it being one of the creationists' targets when trying to show that evolution is untenable. But these are actually two very good reasons for bringing up the subject, and I hope that, even in such a complicated subject, I've managed to write so as to increase understanding.
The topic isn't finished; there are other aspects that need dealing with. For now, the best place to start is with the distinction between the various types of thermodynamic systems. It's a bit dry, but it's crucial to understanding the rest. Thereafter, we can move straight on to the juicier application of the first and second law of thermodynamics to biology.
Once that's been covered, the next topic to consider under the thermodynamics banner is which reactions are 'spontaneous' or not. The post on enthalpy is the place to start, and the rest is soon to follow...
As an aside, we've also hopefully shown that even a small understanding of thermodynamics is enough to see why the creationists are wrong on this matter. I've appended a summary article I found on this topic, and a physicist also recently put some figures to the whole process, so you can find out just how many million times the creationists are wrong.