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Cell Membranes Problem Set

Problem 8: Cotransport


Cotransport systems of the intestinal epithelial cells include the_________ in the intestine facing membrane, the energy requiring _____________ facing the blood, and the ______________allowing facilitated diffusion of glucose out of the cell.

A. permease, cotransporters, Na+K+ ATPase
B. cotransporters, CFTR, permeases
C. Na+K+ ATPase, cotransporters, permeases

cotransporters, Na+K+ ATPase, permeases

The Na+K+ ATPase moves Na+ out of the epithelial cells lining the intestine and into the blood. The reduced concentration of Na+ inside the cell coupled with high Na+ inside the lumen of the intestine provides a driving force for the movement of Na+ into the cell.

The co-transporters in the membrane of the epithelial cell facing the intestine allow Na+ to enter only when accompanied by either glucose or one of the amino acids (each have their own set of co-transporters). Glucose then moves into the blood through a permease in the membrane between the cell and the blood. Thus, ATP is used as an energy source to drive Na+ out of the cell resulting in glucose transport from the intestine to our blood.

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