Question

A biochemist wants to control the initial substrate-level phosphorylation that occurs in the tracheal cells of grasshoppers once glucose has crossed the plasma membrane. He has access to the following inhibitors: Rotenone - an electron transport chain inhibitor, Oligomycin - an ATP synthase inhibitor, and TLN-232, an inhibitor of glycolysis. Which inhibitor should he use to slow down initial substrate-level phosphorylation that occurs once glucose has crossed the plasma membrane?

Answer 1

The answer here is TLN-232.

Substrate-level phosphorylation refers to phosphorylation of the substrate (glucose) before generating ATP during glycolysis. By preventing glycolysis, you prevent all the subsequent steps of cellular respiration, including the phosphorylation that occurs during glycolysis.

Rotenone is incorrect because even if you inhibit the ETC, glycolysis has still occurred, and glycolysis includes substrate-level phosphorylation.

Oligomycin is incorrect because ATP synthesis by ATP synthase relies on the phosphorylated substrate to produce ATP. By the time ATP synthase enters the picture, again the substrate has already been phosphorylated.