I recommend keeping this as simple as possible. The simpler the concepts the easier it will be to transcribe them into comic form.
Remembering back to my Bio 102 class, Riboflavin is a B vitamin that helps breakdown fats & proteins and converts them into ATP (usable energy in the body).
Based on that alone, maybe you could make a comic strip about "the B vitamins" and focus on Riboflavin, "the fat smasher" or something idk, and his role is to find fat and protien and "turn them into ATP". and like have a little picture of "fat" and "protien" being smashed and then a picture of "ATP".
I just re-read your OP and yeah, I think you already know what I just wrote^. Idk much more than that, havn't taken Cell Biology yet. Sorry I couldn't help more smile Goodluck!