AMCAS has an FAQ somewhere on the website that explains it really well, but in general, if your undergrad uses a 4.0 scale with typical +/- annotations, then your GPA will be similar and if not, then they'll recalculate it based on their guidelines.
BCPM, rather than course designations, is more of a categorization of "technical" type coursework. That means that anatomy, physio, biochem, etc. will fit under a "Biology" category and be calculated into BCPM. Sometimes it's really ambiguous (like cognitive neuroscience), but for the most part, when you apply, just make your best guess according to the FAQ (which lists general courses and categories. AMCAS will correct anythiing they feel is a mistake when they verify your transcript.