New students must have earned a bachelor's degree that includes general chemistry, organic chemistry, biochemistry, organ level physiology, and general nutrition. You can be accepted without these prerequisites; however, if you can't acquire competency in these areas prior to admission, you may need to take additional courses in these areas in your first year at Purdue. This will likely extend the time it takes for you to complete your degree.
The INP curricula for MS and PhD students were designed to provide maximal flexibility. After completing a core of content and skill building courses, students have a great deal of latitude regarding the specific classes they take and the direction of their training.