you need physiology to understand endocrinology, not biochemistry. Number of people who care that GH-receptors use the tyrosine kinase system? zero. That's real biochemistry, albeit extremely superficial, because it's just a factoid. Real biochemistry would talk about concentrations of growth hormone needed to reach threshold, the kinetics of the tyrosine kinase system, the binding capacities of the GH-receptor and how the cell is able to alter it. Learning real biochemistry enables you to ask pointed research questions. We learn trivia and just like trivia, it's forgotten within a few weeks after learning unless one is deeply invested in the subject. It's learning that Mickey Mantle hit 17 home runs in his first 25 games and saying this tidbit is essential to understanding baseball.
When you get to 3rd year and beyond, you'll understand how much time was wasted in the first 2 years, solely for the purpose of stratifying students on Step 1. The clinicians teaching us medicine didn't even know 70% of the basic sciences existed when they were training. And yet they are the standard of care today.
Looking back at the first 2 years, I'd say knowing physiology, anatomy, microbiology, pharmacology, and pathology/pathophys are what really matters. The rest? Just junk material designed to make med school harder than it has to be.