Question

The cartoon depicts intestinal epithelial cells joined to their neighbors by tight junctions, which allow the cells to maintain biochemically distinct apical and basolateral regions. Which of the following accurately describes “the fence function” of tight junctions in intestinal epithelial cells?

Group of answer choices

(A) The fence function prevents Na+-driven glucose transporters from diffusing to the basolateral side and passive glucose transporters from diffusing to the apical side of the plasma membrane

(B) The fence function prevents mixing of the extracellular fluid from the lumen of the gut from mixing with extracellular fluid of the connective tissue

(C) The fence function fulfills both of the functions described in A and B above

(D) The fence function fulfills neither of the functions in A and B, it is the barrier function of tight junctions that does both of those things

Answer 1

The correct option is A - The fence function prevents Na+ driven glucose transporters from diffusing to the basolateral side and passive glucose transporters from diffusing to the apical side of the plasma membrane

The fence function of the tight junction prevents the mixing up of material between the domains of the plasma membrane of the epithelial cells (apical and basolateral membrane domains). The fence function of the tight junction maintains cell polarity by preventing the mixing up of molecules and ions between the apical and basolateral cell surface. Fence function prevents the apical molecules from diffusing to the basolateral side and basolateral molecules from diffusing to the apical side. Sodium driven glucose transporters (SGLTs) are found in the apical membrane and passive glucose transporters (GLUTs) are found in the basolateral membrane. Fence function of the tight junction prevents the movement of membrane proteins from the apical cell surface to the basolateral cell surface and vice versa

Hence, the correct option is A