MCAT Question A Day - 7/27/13 - Answer!
The nephrons of the kidney filter glucose from the blood while wastes are being removed. The nephron tubules then have the responsibility of reabsorbing the glucose molecules back into the circulation. The reabsorption of glucose by the kidney tubules would be expected to proceed by which of the following?
A. Osmosis
B. Diffusion
C. Facilitated diffusion
D. Active transport
The correct answer is (D). Since the amount of glucose filtered out of the blood is significantly less than the total amount of glucose remaining in the blood, the reabsorption of glucose involves moving it from where there is less (the urinary filtrate) to where there is more (circulation). This would require active transport and the expenditure of ATP.
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