Choose the incorrect match .

Options

A. Primary messenger : Calcium ion
B. Insulin : Peptide hormone
C. Erythropoietin : Formation of RBC
D. Aldosterone : Steroid

Answer

To solve the question of identifying the incorrect match, we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Aldosterone**:
- Aldosterone is classified as a steroid hormone.
- Its primary function is to regulate salt and water balance in the body, which in turn affects blood pressure.
- **Conclusion**: This match is correct.

2. **Erythropoietin**:
- Erythropoietin is a hormone that stimulates the production of red blood cells (RBCs).
- The process of RBC production is known as erythropoiesis, which occurs in the bone marrow and is indeed regulated by erythropoietin.
- **Conclusion**: This match is correct.

3. **Insulin**:
- Insulin is a hormone that is indeed classified as a peptide hormone.
- It is composed of two polypeptide chains (A and B) linked by disulfide bonds.
- **Conclusion**: This match is correct.

4. **Calcium Ion**:
- Calcium ions (Ca²⁺) are often referred to as secondary messengers in cellular signaling pathways.
- Primary messengers are typically hormones or other signaling molecules that bind to receptors on the cell surface, while secondary messengers relay the signal inside the cell.
- **Conclusion**: This match is incorrect.

### Final Answer:
The incorrect match is **Calcium ion as a primary messenger**.

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