Hey Beansprout,
I did a Bio degree post-bac at UA and finished in 2003. I had tons of pre-pharm people in my basic sciences, and I can tell you that there is not much grade inflation in the science classes. There were definitely people who got C's, D's, or failed, especially in Gen Chem, O-Chem, and Physics. Class averages in some classes were like 35-45, and if you got that average you would get a C, even if the professor curved the grades. A lot depends on the professor. Some offered some extra credit, but probably not enought to make a significant difference in your final grade. If you work hard, and have a decent professor, you'll be fine. But don't worry, the classes will definitely weed people out. I saw many people go in premed or pre-pharm and drop that path before getting through the basic sciences.
The grading system is A, B, C, etc. with no pluses or minuses. This is great if you get a 90 avergae and get an A instead of an A-, but sux if you have an 89 average and get the same grade as someone who got an 80 and did half the work you did. But it all evens out in the end. I think some lab sections, depending on the TA, have more grade inflation because in many of my labs, as long as you showed up and turned in something, you'd get a B. Feel free to PM me if you have any questions about UA or professors or whatever. Good luck 🙂
