Second messenger is

Options

A. ATP
B. cAMP
C. GTP
D. ATP and AMP

Answer

**Step-by-Step Solution:**

1. **Understanding Second Messengers**:
- Second messengers are low molecular weight compounds that play a crucial role in cellular signaling. They help in transmitting and amplifying signals from hormones or other signaling molecules to initiate a response within the cell.

2. **Role of Second Messengers**:
- These molecules act as intermediaries in the signaling pathways, facilitating the activation of downstream enzymes and triggering a cascade of biochemical reactions within the cell.

3. **Analyzing the Options**:
- The options provided are ATP, CMP, GTP, ATP, and AMP. We need to identify which of these is a second messenger.
- ATP (Adenosine Triphosphate) and GTP (Guanosine Triphosphate) are primarily known as energy carriers in the cell, not as second messengers.
- AMP (Adenosine Monophosphate) is formed when ATP loses two phosphate groups, but it is not typically classified as a second messenger.

4. **Identifying the Correct Second Messenger**:
- The most well-known second messenger is cyclic AMP (cAMP). It is derived from ATP and plays a significant role in various signaling pathways, especially in response to hormones.

5. **Conclusion**:
- Based on the analysis, the correct answer to the question "Second messenger is" would be cyclic AMP (cAMP).

**Final Answer**: The second messenger is cyclic AMP (cAMP).

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