Once glucose has entered a cell, what prevents it from diffusing back out of the cell?
A) Glucose pumps actively transported any leaked glucose back into the cell.
B) One side of the cell membrane is permeable to glucose, but the other side is not.
C) Glucose inhibitors attach to glucose once it's in the cell.
D) Glucose is phosphorylated, preventing it from leaving the cell.
E) Glucose is hydrolyzed into two three-carbon molecules that cannot diffuse in a reverse direction.

Question

​Once glucose has entered a cell, what prevents it from diffusing back out of the cell?
A) ​Glucose pumps actively transported any leaked glucose back into the cell.
B) ​One side of the cell membrane is permeable to glucose, but the other side is not.
C) ​Glucose inhibitors attach to glucose once it's in the cell.
D) ​Glucose is phosphorylated, preventing it from leaving the cell.
E) ​Glucose is hydrolyzed into two three-carbon molecules that cannot diffuse in a reverse direction.

Quizplus · Accepted Answer

Glucose is phosphorylated to glucose-6-phosphate by the enzyme hexokinase in most cells (or glucokinase in liver and pancreatic cells). This phosphorylation traps glucose within the cell because the glucose-6-phosphate cannot easily cross the cell membrane, effectively preventing it from diffusing back out of the cell.

​Once Glucose Has Entered a Cell, What Prevents It from Diffusing

Once Glucose Has Entered a Cell, What Prevents It from Diffusing