Aspects of Michaelis-Menten that are discussed in 1st-yr bio can come up and they COULD put a passage on a real MCAT, but I haven't seen anything like it on one. (Although I do recall having a discrete that required an understanding of Vmax.) Regardless, it's good to understand. Basically, just understand the relationships between , Vmax, rate, competitive and noncompetitive inhibition (uncompetitive is outside the scope of the MCAT). You should be able to quickly identify a graph of the two former inhibition types. Also, understand general catalysis (what it is does/not do) and be able to recognize all components of a rxn (catalysts, products, reactants). Be able to identify what component a molecule is likely to be based on experimental data, etc.