Poisons like cyanide inhibit `Na^(+)` influx during cellular transport. This inhibitory effect is reversed by an injection of ATP. This demonstrates that

Options

A. `Na^+ - K^+` pump operates in all cells
B. ATP is carrier protein
C. Energy for `Na^+ -K^+` pump come from ATP
D. ATP is hydrolysed by ATPase to release energy

Answer

To solve the question regarding the effect of cyanide on sodium influx during cellular transport and how this effect can be reversed by ATP injection, we can break it down into several steps:

### Step-by-Step Solution:

1. **Understanding the Role of Sodium and Potassium Pump**:
- The sodium-potassium pump (Na+/K+ ATPase) is crucial for maintaining the electrochemical gradient across the cell membrane. It typically expels 3 sodium ions (Na+) out of the cell and brings in 2 potassium ions (K+) into the cell, which is essential for cellular function.

**Hint**: Recall the function of the sodium-potassium pump and its importance in maintaining the cell's resting membrane potential.

2. **Impact of Cyanide**:
- Cyanide is a potent inhibitor of cytochrome oxidase, an enzyme involved in the electron transport chain (ETC) that is necessary for ATP production. By inhibiting this enzyme, cyanide effectively halts ATP synthesis.

**Hint**: Consider how the inhibition of ATP production affects cellular processes that rely on ATP.

3. **Consequences of ATP Depletion**:
- With reduced ATP levels due to cyanide's action, the sodium-potassium pump cannot function properly. This leads to an inability to maintain the sodium and potassium gradients, resulting in disrupted cellular transport and potential depolarization of the cell membrane.

**Hint**: Think about how energy (in the form of ATP) is required for active transport mechanisms like the sodium-potassium pump.

4. **Reversal of Inhibition by ATP Injection**:
- When ATP is injected, it provides the necessary energy for the sodium-potassium pump to resume its function. This allows for the restoration of sodium influx and potassium efflux, reversing the inhibitory effect caused by cyanide.

**Hint**: Reflect on how adding ATP can restore the functionality of a transport mechanism that relies on energy.

5. **Conclusion**:
- The question asks what this demonstrates. The key takeaway is that the sodium-potassium pump requires energy from ATP to function, and its activity can be inhibited by substances like cyanide that disrupt ATP production. Therefore, the correct statement is that the energy for the sodium-potassium pump comes from ATP.

**Final Answer**: The correct conclusion is that the energy for the sodium-potassium pump comes from ATP.

### Summary of Key Points:
- Sodium-potassium pump maintains cell potential.
- Cyanide inhibits ATP production by affecting cytochrome oxidase.
- ATP is necessary for the pump to function.
- Injection of ATP can reverse the inhibitory effects of cyanide.