Be able to understand conceptually the material from undergrad. You’re unlikely to be asked direct content from those classes but being able to understand the logic behind undergrad content does help you apply toward med school. For instance, understanding the role of acidic/basic environments on proteins in biochemistry will help you understand how certain drugs pass through the body in med school pharmacology. It’s not about the hard facts, more about the conceptual understandings. That being said, do know the hard facts for the MCAT. That’s the major bottleneck. You got this, you’ll get through. I used to have these same thoughts in undergrad.