When water is added to a living cell, the following is not observed.

Options

A. Increase in free energy for water
B. Decrease in the amount of solute
C. Increase in pressure potential
D. Increase in water potential

Answer

To solve the question, "When water is added to a living cell, the following is not observed," we need to analyze the options provided and understand the effects of adding water to a living cell.

### Step-by-Step Solution:

1. **Understanding Water Potential**:
- Water potential (Ψ) is the potential energy of water in a system compared to pure water. It is influenced by solute potential (Ψs) and pressure potential (Ψp).
- The formula for water potential is:
\[ Ψ = Ψs + Ψp \]

2. **Effect of Adding Water**:
- When water is added to a living cell, the volume of water inside the cell increases, which affects the water potential.
- An increase in water volume leads to an increase in water potential (Ψ).

3. **Analyzing Each Option**:
- **Increase in Free Energy for Water**:
- When water is added, the free energy of water increases because there is more water available. This option is observed.
- **Decrease in Amount of Solute**:
- Adding water dilutes the solute concentration, but it does not decrease the total amount of solute present in the cell. The mass of solute remains the same, so this option is **not observed**.
- **Increase in Pressure Potential**:
- The addition of water increases the turgor pressure within the cell, leading to an increase in pressure potential. This option is observed.
- **Increase in Water Potential**:
- Since more water is added, the water potential increases. This option is also observed.

4. **Conclusion**:
- The only statement that is not observed when water is added to a living cell is the "decrease in amount of solute." The amount of solute remains constant, even though its concentration may decrease.

### Final Answer:
The following is not observed when water is added to a living cell: **Decrease in amount of solute**.