Bertybassett
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Im really confused with this. So I know that it is active transport, yet many sources say that it doesn't actually require ATP? In the exam (AQA a level bio), should I just say that it uses ATP?
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ctchannah
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are you talking about in the ileum
and yes its active transport bcuz sodium goes down its conc gradient and glucose goes against it conc gradient
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Jpw1097
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(Original post by Bertybassett)
Im really confused with this. So I know that it is active transport, yet many sources say that it doesn't actually require ATP? In the exam (AQA a level bio), should I just say that it uses ATP?
No, the transporter itself does not use ATP however, it is still a form of active transport (secondary active transport to be precise). That's because the sodium-glucose cotransporter is located on the apical membrane (i.e. the membrane closest to the lumen). The transporter uses the sodium concentration gradient (sodium moves from high concentration within the lumen to low concentration within the cell) to drive glucose into the cell against its concentration gradient (i.e. from low to high concentration). The transporter itself does not use ATP, however, in order to generate the sodium concentration gradient (high sodium in the lumen, low sodium in the cell), the sodium-potassium pump pumps three sodium ions out of the cell in exchange for two potassium ions - this keeps the sodium concentration very low inside the cell, maintaining the concentration gradient. The sodium-potassium pump is located on the basolateral membrane (the membrane closest to the capillaries) and uses ATP.
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