Which is true for excretion in humans

Options

A. Glucose and amino acids are reabsorbed in PCT by simple diffusion
B. DCT is impermeable to water
C. On the average, `25- 30` gm of urea is excreted per day
D. Maximum reabsorption occurs in loop of Henle's

Answer

To determine which statement is true regarding excretion in humans, let's analyze each of the four statements provided:

1. **Statement 1**: Glucose and amino acids are reabsorbed in PCT by simple diffusion.
- The proximal convoluted tubule (PCT) is responsible for reabsorbing a significant portion of the glomerular filtrate. However, glucose and amino acids are reabsorbed through **secondary active transport**, not simple diffusion. Therefore, this statement is **incorrect**.

2. **Statement 2**: DCT is impermeable to water.
- The distal convoluted tubule (DCT) is relatively impermeable to water, but it is not completely impermeable. It can still allow some water to pass through under certain conditions, especially when influenced by hormones like aldosterone. Thus, this statement is also **incorrect**.

3. **Statement 3**: On average, 25 to 30 grams of urea is excreted per day.
- Urea is a primary nitrogenous waste product in humans, and it is indeed excreted in the range of about 25 to 30 grams per day. This aligns with the known physiological data about human excretion. Therefore, this statement is **correct**.

4. **Statement 4**: Maximum reabsorption occurs in the loop of Henle.
- The maximum reabsorption of water and solutes occurs in the proximal convoluted tubule (PCT), not in the loop of Henle. Therefore, this statement is **incorrect**.

Based on the analysis above, the correct answer is that **Statement 3 is true**: On average, 25 to 30 grams of urea is excreted per day.