Given below are steps involved in the mechanism of action of hormones. Arrange them in proper sequence and select the correct option.
I. Formation of the hormone - receptor complex .
II. Biochemical changes in the target cell.
III. Binding of the hormone with the receptor.
IV. Physiological responses in the target cell.

Options

A. II, I, IV, III
B. III,I,II,IV
C. III,I,II,IV
D. I, III , IV , II

Answer

To solve the question regarding the mechanism of action of hormones, we need to arrange the given steps in the proper sequence. Let's analyze the steps provided:

1. **Formation of the hormone-receptor complex.**
2. **Biochemical changes in the target cell.**
3. **Binding of the hormone with the receptor.**
4. **Physiological responses in the target cell.**

### Step-by-Step Solution:

**Step 1: Binding of the hormone with the receptor (III)**
- The first step in the mechanism of action of hormones is the binding of the hormone to its specific receptor on the target cell. This is crucial as it initiates the signaling process.

**Step 2: Formation of the hormone-receptor complex (I)**
- Once the hormone binds to the receptor, a hormone-receptor complex is formed. This complex is essential for the subsequent steps in the signaling pathway.

**Step 3: Biochemical changes in the target cell (II)**
- The formation of the hormone-receptor complex triggers biochemical changes within the target cell. These changes can include activation of enzymes, alteration of gene expression, or changes in ion channel activity.

**Step 4: Physiological responses in the target cell (IV)**
- Finally, these biochemical changes lead to physiological responses in the target cell, which can manifest as changes in metabolism, growth, or other cellular functions.

### Final Sequence:
The correct sequence of steps is:
- III (Binding of the hormone with the receptor)
- I (Formation of the hormone-receptor complex)
- II (Biochemical changes in the target cell)
- IV (Physiological responses in the target cell)

Thus, the correct order is: **III → I → II → IV**.

### Correct Option:
The correct option based on the sequence is **3rd: III, I, II, IV**.

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