In heart cells, which one serves as a second messenger, speeding up muscle cell contraction in respone to adrenaline ?

Options

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

Answer

To answer the question regarding which molecule serves as a second messenger in heart cells that speeds up muscle cell contraction in response to adrenaline, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Role of Adrenaline**:
- Adrenaline, also known as epinephrine, is a hormone released from the adrenal medulla. It plays a crucial role in the "fight or flight" response and affects various tissues, including heart muscle cells.

**Hint**: Remember that adrenaline is a hormone that influences heart function.

2. **Mechanism of Action**:
- Adrenaline binds to specific receptors on the surface of heart muscle cells (adrenergic receptors). This binding triggers a cascade of intracellular events.

**Hint**: Focus on how hormones interact with cell receptors to initiate a response.

3. **Role of Second Messengers**:
- When adrenaline binds to its receptor, it activates a G-protein, which in turn stimulates the enzyme adenylate cyclase. This enzyme converts ATP (adenosine triphosphate) into cyclic AMP (cAMP).

**Hint**: Identify the key enzyme that is activated by the hormone-receptor interaction.

4. **Cyclic AMP (cAMP) as a Second Messenger**:
- cAMP acts as a second messenger within the cell. It amplifies the signal from adrenaline and leads to increased calcium ion levels in the heart muscle cells, which enhances muscle contraction.

**Hint**: Recall that second messengers amplify the effects of the primary signal (in this case, adrenaline).

5. **Conclusion**:
- Based on the above steps, we conclude that the molecule serving as a second messenger that speeds up muscle cell contraction in response to adrenaline in heart cells is cyclic AMP (cAMP).

**Final Answer**: The correct option is **C - cAMP**.