When a cell contains some nondiffusible or fixed ions which are kept balanced by diffusible ions of opposite charge , this condition is known as

Options

A. Donnan equilibrium
B. Chemical equilibrium
C. Saturation effect
D. Ionic exchange

Answer

To answer the question about the condition when a cell contains some non-diffusible or fixed ions that are balanced by diffusible ions of opposite charge, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Terms**:
- **Non-diffusible or Fixed Ions**: These are ions that cannot move freely across the cell membrane. They are often large or charged molecules that remain in place.
- **Diffusible Ions**: These are ions that can move across the cell membrane, typically smaller ions that can pass through channels or pores.

2. **Identifying the Condition**:
- The question describes a situation where the non-diffusible ions are balanced by diffusible ions of opposite charge. This indicates a specific type of equilibrium where the concentration of ions is maintained.

3. **Recognizing the Concept**:
- This condition is known as **Donnan Equilibrium**. It is a state of equilibrium that occurs when a semi-permeable membrane separates two solutions containing ions of different charges. The non-diffusible ions create an imbalance that is countered by the movement of diffusible ions.

4. **Eliminating Other Options**:
- **Chemical Equilibrium**: This refers to a state where the rate of the forward reaction equals the rate of the backward reaction, which does not specifically relate to the presence of fixed and diffusible ions.
- **Saturation Effect**: This describes a decrease in intensity of spectral lines with increased external electromagnetic radiation, unrelated to ion balance.
- **Ion Exchange**: While this involves the exchange of ions, it does not specifically refer to the balance of fixed and diffusible ions.

5. **Conclusion**:
- Based on the definitions and the specific conditions described, the correct answer to the question is **Donnan Equilibrium**.

### Final Answer:
The condition is known as **Donnan Equilibrium**.