one word of advice, get the ek bio book in order to review bio as a supplement to the tpr book cause the tpr book misses a lot of critical concepts that do show up on the mcat. on my test day the mcat covered granulocytes and agranulocytes, if i had just relied on tpr..i wouldn't know what the hell they were talking about, but i had reviewed immune system in EK as well and was thankfully saved by that. make sure you definitely cover your weakest bio sections with both tpr and EK.
as far as bio being overwhelming...it is because the curve is steep due to all the bio and science majors that take this exam. you have to master one concept at a time and make sure you constantly, constantly review the material while you are moving on to new bio concepts. i know its deftly laborious, but there is absolutely no way around this. for orgo memorize till your eyeballs fall out and be familiar with the material in ANY CONTEXT. for example, be able to recognize an aldol condensation even with a wierd looking ketone...bottom line is to always boil down information to the simplest concepts when it comes to orgo.