Which of the following substances is not filtered into the cavity of Bowman's capsule?

Options

A. Urea
B. Amino acids
C. Glucose
D. Plasma proteins

Explanation

To determine which substance is not filtered into the cavity of Bowman's capsule, we need to analyze the substances listed: urea, amino acids, glucose, and plasma proteins.

### Step-by-Step Solution:

1. **Understanding Bowman's Capsule**: Bowman's capsule is a crucial part of the nephron in the kidney. It is responsible for the initial filtration of blood to form urine.

2. **Composition of Filtrate**: The filtrate that enters Bowman's capsule has a composition similar to that of blood plasma. However, certain components of blood plasma do not pass into the filtrate.

3. **Components of Blood Plasma**: Blood plasma contains various substances, including:
- Urea
- Amino acids
- Glucose
- Plasma proteins
- Red blood cells (RBCs)

4. **Size and Filtration**: The filtration process in Bowman's capsule relies on size exclusion. Substances that are too large cannot pass through the filtration barrier into the capsule.

5. **Analyzing the Substances**:
- **Urea**: Small enough to be filtered.
- **Amino Acids**: Small enough to be filtered.
- **Glucose**: Small enough to be filtered.
- **Plasma Proteins**: Generally too large to be filtered due to their size.

6. **Conclusion**: Among the options provided, plasma proteins are not filtered into the cavity of Bowman's capsule because they are too large to diffuse through the filtration barrier.

### Final Answer:
**Plasma proteins are not filtered into the cavity of Bowman's capsule.**