Question

GLUTs are integral membrane proteins that assist in the facilitated diffusion of glucose into and out of cells. What reaction in glycolysis prevents glucose from being transported back out of the cell?

a) Conversion of glucose to glucose-6-phosphate
b) Formation of pyruvate from phosphoenolpyruvate
c) Production of ATP from ADP
d) Oxidation of glyceraldehyde-3-phosphate

Answer 1

The conversion of glucose to glucose-6-phosphate by hexokinase is the reaction in glycolysis that prevents glucose from being transported back out of the cell since phosphorylated glucose cannot easily cross the cell membrane.

Step-by-step explanation:

The reaction in glycolysis that prevents glucose from being transported back out of the cell is the conversion of glucose to glucose-6-phosphate. This irreversible step is catalyzed by the enzyme hexokinase and uses one molecule of ATP.

The phosphorylation of glucose to form glucose-6-phosphate is significant because the phosphorylated glucose molecule cannot easily cross the cell membrane. It therefore remains trapped within the cell, effectively ensuring that the cell retains glucose for its metabolic needs. The glucose transporters or GLUTs facilitate the movement of glucose across the cell membrane, but once glucose is phosphorylated, it cannot be transported back out by these GLUTs.