Substrate which is not readsorbed in urine is

Options

A. Carbohydrates
B. Fats
C. Vitamins
D. Proteins

Answer

To determine which substrate is not reabsorbed in urine, we need to analyze the options provided: carbohydrates, fats, vitamins, and proteins.

### Step-by-Step Solution:

1. **Understanding Reabsorption in the Kidneys:**
- The kidneys filter blood to produce urine, and during this process, certain substances are reabsorbed back into the bloodstream while others are excreted.

2. **Analyzing Each Option:**
- **Carbohydrates:**
- The primary carbohydrate in the blood is glucose. Glucose is 100% reabsorbed in the renal tubules under normal conditions. Therefore, carbohydrates are not the correct answer.

- **Fats:**
- Fats are generally insoluble in water and are not typically found in urine. They are not filtered through the kidneys in significant amounts and thus are not reabsorbed. However, they are not excreted in urine. Hence, fats are not the correct answer.

- **Vitamins:**
- Vitamins can be categorized into water-soluble (like vitamin B and C) and fat-soluble (like vitamins A, D, E, and K). Water-soluble vitamins are often excreted in urine when in excess, and some, like vitamin B and C, are not reabsorbed effectively. Therefore, vitamins could be a potential answer.

- **Proteins:**
- Proteins are typically too large to be filtered through the glomerulus of the kidneys and are not found in urine under normal circumstances. If present, they are usually reabsorbed. Thus, proteins are not the correct answer.

3. **Conclusion:**
- Based on the analysis, the substrate that is not reabsorbed in urine is **vitamins**, particularly water-soluble vitamins like vitamin B and C.

### Final Answer:
The substrate which is not reabsorbed in urine is **vitamins**.

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