Question. Passage: "Arsenate, a derivative of arsenic, is a deadly poison that acts as a substrate for glyceraldehyde 3-phosphate dehydrogenase." Question: The action of arsenate on glyceraldehyde 3-phosphate dehydrogenase is best described as: A. competitive inhibition B. noncompetitive inhibition C. allosteric inhibition D. negative feedback Based on the passage alone, you cannot distinguish if the inhibition is competitive or noncompetitive, correct? I think the way to answer this question is to look at the answer choices. D cannot be correct. According to EK, "You will not be asked to distinguish allosteric inhibition from noncompetitive inhibition on the MCAT." First off is this statement true? If so, then B and C are the same choice, and by process of elimination A must be correct. Does "substrate" imply a substrate at the active site and therefore competitive inhibition? Or do you call molecules that bind at places other than the active site (noncompetitive inhibitors) 'substrates' as well?