Need help in biology question, please explain me in detail. Thank you so much. T

Question

Need help in biology question, please explain me in detail. Thank you so much.

The kidney is a complex organ that consists of millions of renal tubules. Each renal tubule has a lumen. Blood is filtered in the kidneys; cells and large proteins found in the blood remain in the blood, while water and numerous small solutes enter the lumen of the renal tubules. The cells that line the renal tubules reabsorb most of these nutrients and put them back in the blood. The cells of the proximal convoluted tubule reabsorb glucose out of the renal tubule. How might this work? Consider that the concentration of sodium ions in blood is approximately 140 mM.

Explanation / Answer

1. Glucose is a polar molecule, not soluble in the plasma membrane and transported across by carrier protein called glucose transporters.

2. There are two glucose transporters. They are 1) The facilitative diffusion glucose transporters (GLUTs)

2) The Na+/glucose co-transporters (SGLTs)

3. Under normal conditions, if tubular glucose load is approximately 120mg/min or less, there is no glucose loss in urine.

4. However, when the glucose level exceeds 220mg/min glucose starts to appear in the urine.

5. 90% of glucose is reabsorbed by the high absorption capacity of 2 sodium-glucose co-transporter in convoluted segment of proximal tubule and 10 of glucose is reabsorbed by SGLT1 transporter in the straight segment of the descending proximal tubule.

6. As SGLT1 co-transporter transports 2:1 of Na+/Glucose, If the concentration of sodium ions in blood is approximately 140 mM, 70mg/min is transported across the PCT.

7. As SGLT2 co-transporter transports 1:1 of Na+/Glucose, 140mg/min is transported across the PCT.

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