Which is correctly categorised

Options

A. Troponin and Myosin-Complex proteins in striated muscles
B. Calcitonin and Thymosin-Thyroid hormones
C. Pepsin and Prolactin-Digestive enzymes secreted in stomach
D. Secretin and Rhodopsin-Polypeptide hormones.

Answer

To solve the question "Which is correctly categorized?", we need to analyze each option provided and determine if the categorization is accurate.

### Step-by-Step Solution:

1. **Understanding Troponin and Myosin**:
- Troponin is a complex of three regulatory proteins that play a crucial role in muscle contraction, specifically in skeletal and cardiac muscles.
- Myosin is a type of motor protein that is essential for muscle contraction and is involved in various motility processes.

**Conclusion**: Troponin and myosin are correctly categorized as proteins involved in muscle contraction.

2. **Analyzing Calcitonin and Thymosin**:
- Calcitonin is a hormone produced by the thyroid gland that helps regulate calcium levels in the blood.
- Thymosin is a hormone produced by the thymus gland that is involved in the development of T-cells (a type of white blood cell).

**Conclusion**: Calcitonin and thymosin are not both thyroid hormones; thus, this categorization is incorrect.

3. **Evaluating Pepsin and Prolactin**:
- Pepsin is a digestive enzyme that is secreted in the stomach and is responsible for breaking down proteins.
- Prolactin, however, is a hormone primarily involved in lactation and is not a digestive enzyme.

**Conclusion**: Pepsin and prolactin are incorrectly categorized as digestive enzymes secreted in the stomach.

4. **Reviewing Secretion and Rhodopsin**:
- Secretion generally refers to the process of producing and releasing substances like hormones or enzymes.
- Rhodopsin is a light-sensitive receptor protein involved in visual phototransduction in the retina, not a polypeptide hormone.

**Conclusion**: Secretion and rhodopsin are incorrectly categorized as polypeptide hormones.

### Final Answer:
The correctly categorized pair is **Troponin and Myosin complex protein in striated muscles**.

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