Cells lining the small intestine absorb glucose. Which of the following is required to transport glucose molecules across the cell membranes of the intestine?
Absorption of Glucose and Other Monosaccharides: Transport Across the Intestinal Epithelium Absorption of glucose entails transport from the intestinal lumen, across the epithelium and into blood. The transporter that carries glucose and galactose into the enterocyte is the sodium-dependent hexose transporter, known more formally as SGLUT-1. As the name indicates, this molecule transports both glucose and sodium ion into the cell and in fact, will not transport either alone. The essence of transport by the sodium-dependent hexose transporter involves a series of conformational changes induced by binding and release of sodium and glucose, and can be summarized as follows: 1. the transporter is initially oriented facing into the lumen - at this point it is capable of binding sodium, but not glucose 2. sodium binds, inducing a conformational change that opens the glucose-binding pocket 3. glucose binds and the transporter reorients in the membrane such that the pockets holding sodium and glucose are moved inside the cell 4. sodium dissociates into the cytoplasm, causing glucose binding to destabilize 5. glucose dissociates into the cytoplasm and the unloaded transporter reorients back to its original, outward-facing position http://www.vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/absorb_sugars.html
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