Lucky for you and me, the MCAT doesn't require the we memorize all the enzyme names and structures of the intermediates in glycolysis. Heck, we don't even really need to memorize the order of the pathway save the inputs and outputs. Glycolysis is an extremely old pathway and is the universal first step in glucose metabolism--all cells from all domains possess the enzymes of this pathway. In short, a glucose molecule is oxidized and split into two pyruvate molecules producing a net surplus of 2 ATP and 2 NADH. It also takes place in the cytoplasm. Hexokinase catalyzes the first step in glycolysis, the phosphorylation of glucose to G6P. As a side note, anytime you see the word "kinase" think transfer of a phosphate group. Phosphofructokinase (PFK) catalyzes the third step, the transfer of a phosphate group from ATP to F6P to form F16bP. This is an important step in the pathway because the reaction is very favorable (a.k.a. irreversible). In addition, the PFK reaction is the primary control point for glycolysis and is known in many MCAT books as the committed step. As a general rule, very favorable steps in enzymatic pathways are the ones that are usually subject to allosteric regulation--PFK is no exception and is regulated by ATP. High concentrations of ATP inhibit PFK.