Arrange the following mechanism of receptor and chemical messenger in the correct order
I.Receptor regains structure after removal of chemical messengers
II.Receptor receives chemical messenger
III.Shape of receptor changed after attachment of messenger
Choose the correct option

Options

A. I,II and III
B. III,Ii And I
C. III and I,II
D. II,III and I

Answer

To solve the question regarding the correct order of the mechanism of receptor and chemical messenger, we need to analyze the statements provided and arrange them logically based on the process involved.

### Step-by-Step Solution:

1. **Identify the Role of the Receptor and Chemical Messenger**:
- A receptor is a protein that receives chemical signals (chemical messengers). The chemical messenger binds to the receptor, initiating a response in the cell.

2. **Analyze the Statements**:
- **Statement I**: "Receptor regains structure after removal of chemical messengers."
- **Statement II**: "Receptor receives chemical messenger."
- **Statement III**: "Shape of receptor changed after attachment of messenger."

3. **Determine the Sequence**:
- The first step in the process is when the receptor **receives the chemical messenger**. This corresponds to **Statement II**.
- Once the receptor has received the chemical messenger, it undergoes a change in shape to accommodate the messenger. This is described in **Statement III**.
- Finally, after the chemical messenger is removed, the receptor **regains its original structure**. This is outlined in **Statement I**.

4. **Arrange the Statements**:
- Based on the analysis, the correct order of the statements is:
- **II** (Receptor receives chemical messenger)
- **III** (Shape of receptor changed after attachment of messenger)
- **I** (Receptor regains structure after removal of chemical messengers)

5. **Final Answer**:
- The correct order is **2, 3, 1**. Therefore, the correct option is option number 4.