Read the following statements and choose the correct option w r t catecholamines (a) Water soluble hormones which interact with the membrane bound receptors (b) Work through second messenger (c) Binds to external domain of the extracellular receptor present on cell surface (d) They form hormone-receptor complex on the cell surface

Options

A. a and b only
B. b and c only
C. a, c and d only
D. a, b, c and d

Answer

To solve the question regarding catecholamines, we will analyze each statement provided and determine whether they are correct or not.

1. **Statement (a)**: "Water soluble hormones which interact with the membrane bound receptors."
- **Analysis**: Catecholamines, such as epinephrine and norepinephrine, are indeed water-soluble hormones. They do not pass through the cell membrane but instead bind to receptors located on the cell surface (membrane-bound receptors).
- **Conclusion**: This statement is correct.

2. **Statement (b)**: "Work through second messenger."
- **Analysis**: Catecholamines activate second messenger systems within the cell. When they bind to their receptors, they trigger a cascade of events that often involves the production of secondary messengers like cyclic AMP (cAMP) or inositol triphosphate (IP3).
- **Conclusion**: This statement is correct.

3. **Statement (c)**: "Binds to external domain of the extracellular receptor present on cell surface."
- **Analysis**: Catecholamines bind to the external domain of their respective receptors, which are located on the extracellular surface of the cell membrane. This binding is crucial for initiating the signaling cascade.
- **Conclusion**: This statement is correct.

4. **Statement (d)**: "They form hormone-receptor complex on the cell surface."
- **Analysis**: When catecholamines bind to their receptors, they do indeed form a hormone-receptor complex on the cell surface. This complex is essential for the subsequent signaling processes.
- **Conclusion**: This statement is correct.

After analyzing all the statements, we can conclude that all of them (a, b, c, and d) are correct regarding catecholamines.

### Final Answer:
All statements (a, b, c, and d) are correct.

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