Qualifying Exam

In chemistry we didn't have qualifying or cumulative exams. We took an entrance exam and that was great. We also had other things but no qual. or cum. In my new department, we have a qualifying exam. It is three hours of oral grilling by three to four professors. I will be tested on biochemical nutrition, chemistry, and microbiology. There will probably also be a good amount of safety and regulation thrown in because I have had more than the normal number of hours in that area. I am a bit freaked out because I don't know what to expect. Nobody wants to look bad or stupid in front of people they respect but the point is for them to identify what I know and what I don't know. Basically, they are going to grill me until I break. I don't know how that is going to work for me because I can be pretty defensive about my knowledge base. I really don't want to get into a fight with my professors. Not a good way to facilitate relationships.