The increases in which of these properties doesn't increase the rate of diffusion of a gas across alveoli ?

Options

A. Solubility
B. Partial pressure gradient
C. Thickness of respiratory membrane
D. All of these

Answer

To solve the question regarding which property does not increase the rate of diffusion of a gas across the alveoli, we will analyze the options provided.

### Step-by-Step Solution:

1. **Understanding Diffusion**:
- Diffusion is the process by which gas molecules move from an area of higher concentration to an area of lower concentration. In the context of the alveoli, this involves the exchange of oxygen and carbon dioxide.

2. **Identifying the Factors Affecting Diffusion**:
- The rate of diffusion is influenced by several factors:
- **Solubility**: The ability of a gas to dissolve in a liquid. Higher solubility increases diffusion.
- **Partial Pressure Gradient**: The difference in partial pressures of the gases on either side of the membrane. A greater difference increases diffusion.
- **Thickness of the Respiratory Membrane**: The distance that gases must travel. Increased thickness decreases diffusion.

3. **Analyzing Each Option**:
- **Solubility**: If solubility increases, the rate of diffusion also increases because more gas can enter the liquid phase.
- **Partial Pressure Gradient**: An increase in the partial pressure gradient means a stronger driving force for diffusion, thus increasing the rate.
- **Thickness of Respiratory Membrane**: If the thickness increases, the diffusion distance increases, which decreases the rate of diffusion.

4. **Conclusion**:
- Among the options given, the increase in the **thickness of the respiratory membrane** does not increase the rate of diffusion. In fact, it decreases the rate of diffusion due to the increased distance that gases must travel.

### Final Answer:
The increase in **thickness of the respiratory membrane** does not increase the rate of diffusion of a gas across the alveoli.

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