Action of the peptide hormone on a target cell is mediated by

Options

A. A cytoplasmic receptor
B. Cyclic AMP
C. ATP
D. Epinephrin

Explanation

**Step-by-Step Solution:**

1. **Understanding Peptide Hormones**: Peptide hormones are a type of hormone made up of amino acids. They are generally water-soluble and cannot easily cross the cell membrane.

2. **Binding to Receptors**: Because peptide hormones are water-soluble, they bind to specific receptors located on the surface of target cells rather than entering the cells.

3. **Activation of Secondary Messengers**: Upon binding to the receptor, the peptide hormone activates a signaling cascade inside the cell. This often involves the generation of secondary messengers.

4. **Role of Cyclic AMP**: One of the most common secondary messengers produced in response to peptide hormone binding is cyclic AMP (cAMP). This molecule plays a crucial role in transmitting the signal from the receptor to various intracellular processes.

5. **Other Secondary Messengers**: In addition to cAMP, other secondary messengers such as cyclic GMP (cGMP) and calcium ions can also be generated, depending on the specific hormone and receptor involved.

6. **Conclusion**: Therefore, the action of peptide hormones on target cells is mediated by the binding of the hormone to cell surface receptors, which then activate secondary messengers like cAMP, cGMP, or calcium ions.

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