I came across this exam question:
Sodium ions from salt (sodium chloride) are absorbed by cells lining the gut.
Some of these cells have membranes with a carrier protein called NHE3.
NHE3 actively transports one sodium ion into the cell in exchange for one proton
(hydrogen ion) out of the cell.
Use your knowledge of transport across cell membranes to suggest how NHE3
does this.
The mark scheme says that it's co-transport and uses ATP, however I thought co-transport doesn't use ATP?
Thanks.