Have you taken biochemistry? Biochem is one of the worst courses you can take in undergrad. In medical school, we had to learn all of it in two and a half weeks. And then all of immunology (another wonderful course from undergrad) in another two and a half weeks. Add in a week of basic hematology. Know all of it, and be ready for a test on all of it at once that is four hours long, with no breaks whatsoever. If you fail the test (anything below a 70), you're on probation. If you fail another test, you're out. And that's just half of our courses- the other half in first year was gross anatomy, embryology, histology, and clinical skills, which you took concurrently with the systems-based courses. So not only do you have to know all of biochem, hematology basics, and immunology in a six week span, but you're learning it at the same time as the thorax (heart and lungs, lymphatics, muscles, all of it), how to do a full cardiac and respiratory history and physical, week 10-16 embryology, thorax specific embryology, and histology relevant to the block.
Then comes block week. Four hour anatomy test on Monday. Four hour clinical skills exam sometime between Tuesday and Thursday. Four hour exam on heme/immuno/biochem on Friday. Fail anything once, you remediate. Fail a second thing during the year, you're out. And while all this stuff is going on, you've still got mandatory extra visits and things you're required to do- spending a day with a pathologist, or a primary care doctor, or a dentist or whatever so you get an idea of what everyone does in and outside of the hospital. Rinse and repeat five more times, and you're done with the first year of medical school.