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In the cell membrane of the intestinal cells, there is a mobile carrier protein called Sodium Dependent Glucose Transporter(SGLT1).It transports glucose and galactose to inside the cell using energy.The energy is derived from sodium-potassium pump (Primary Active Transport).How it is possible cause we need energy in Na-K pump too ?

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From my initial reading on this, the SGLT1 does not itself directly use energy in the form of ATP. https://en.wikipedia.org/wiki/Sodium-glucose_transport_proteins It appears the uptake of the sugars by this protein are achieved by cotransport. In this case, they "hitch a ride" into intestinal epithelium by following the flow of sodium ions back into the epithelial cells. The reason the Na+ ions flow into the epithelial cells is because of their higher concentration outside the cells. This concentration gradient is created and maintained by the Na-K Pump. So, ATP is used to create a chemical gradient, higher [Na+] outside compared to inside. Then the natural flow of Na+ down its gradient "drags in" the sugars.

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  • $\begingroup$ I still dont get the point . Na-K pump uses the ATP to keep the concentration gradient stable. How the ATP is generated by this pump to be source of energy for SGLT1 mechanism ? $\endgroup$ – Ahmet Öz Nov 24 '16 at 0:26
  • $\begingroup$ The pump uses the energy in ATP to create the gradient. The gradient itself is another form of energy. It is the energy in the gradient that brings in the sugars. Forming a gradient is like blowing up a ballon. Once that balloon is full of air, the compressed air inside wants to rush out. As it does, we can get it to do various chores for us. In this case the higher concentration of Na+ outside the cells is allowed to flow in through the SGLT1. As it does, sugars ride in with the ions. The Na-K Pump keeps pumping Na+ out to keep the process going. $\endgroup$ – bpedit Nov 24 '16 at 1:16

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