Question

Which of the following correctly depicts the mechanism of the Na+/glucose co-transporter discussed in class?

Select one:

a)Both the Na and the glucose must bind which allows Na to move against its gradient because glucose is moving down its gradient.

b)Glucose is pushed against its gradient because Na will be moving with its electrochemical gradient.

c)This transporter binds Na on the outside of the cell, then ATP adds on a Phosphate, which changes the confirmation and open to cells interior where glucose binds. The removal of the Phosphate changes the transporter shape and releases glucose.

d)Both Na and Glucose move with their individual electrochemical gradients when the transporter is open.

Answer 1

The Na+/ glucose co transport is an example of secondary active tranport with both molecules moving in the same direction (symport)

The mechanism of Secondary active transport of these molecules is as follows -

The Na+/K+ ATPase pump functioning at the basolateral membrane of cell pumps 3Na+ out of cell and 2K+ inside the cell (active transport requiring ATP ) creating downhill gradient for Na+ (electrochemical gradient favouring entry into the cell ).

The Na+/ glucose cotransporter utilises this downhill gradient for Na+ to transport glucose uphill (i.e against its electrochemical gradient ) which does not require ATP directly and thus it's called secondary active transport .

Therefore ,the correct option is ( b)-

b) Glucose is pushed against its gradient because sodium will be moving with its electrochemical gradient.