The lectures are specifically aimed at Stage One students. They are a fantastic opportunity for undergraduates to find out how the material covered in lectures fits into the 'bigger picture'.
The lectures are not compulsory, but they will reinforce understanding of core lectures. They are particularly useful if you're thinking about a career in research or medicine.
You'll get a flavour of the world of biomedical research. Download past schedules to get a feel for what the lectures are like: