Question

The reabsorption of glucose in a nephron occurs in

• A. Loop of Henle
• B. First half of proximal tubule
• C. Distal convoluted tubule
• D. Proximal part of collecting ducts

Answer 1

Answer: (B)

First half of proximal tubule

Firstly, the glucose in the proximal tubule is co-transported with sodium ions into the proximal convoluted tubule walls. Some amino acids are also transported in this way. Once in the tubule wall, the glucose and amino acids diffuse directly into the blood capillaries along a concentration gradient. This blood is flowing, so the gradient is maintained. Lastly, sodium/potassium ion active transport pumps remove sodium from the tubule wall and the sodium is put back into the blood. This maintains a sodium concentration gradient in the proximal tubule lining, so the first step continues to happen.

So, the correct answer is option B.