The essential photosynthetic pigment has a ….... at carbon atom 3 of the pyrrole ring - II of chlorophyll a .

Options

A. Methyl group
B. Ethyl group
C. Carboxyl group
D. Magnesium

Answer

To solve the question regarding the essential photosynthetic pigment and the specific group present at carbon atom 3 of the pyrrole ring II of chlorophyll a, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Photosynthetic Pigment**:
- The question refers to chlorophyll a, which is one of the main photosynthetic pigments in plants.

2. **Understand the Structure of Chlorophyll a**:
- Chlorophyll a consists of a porphyrin head made up of four pyrrole rings. Each pyrrole ring has specific carbon atoms that can be substituted with different functional groups.

3. **Locate the Carbon Atom in Question**:
- The question specifically asks about carbon atom 3 of the second pyrrole ring (pyrrole ring II) in chlorophyll a.

4. **Determine the Functional Group at Carbon Atom 3**:
- In chlorophyll a, carbon atom 3 of the second pyrrole ring is substituted with a methyl group (–CH3). This is a distinguishing feature of chlorophyll a compared to chlorophyll b, which has an aldehyde group (–CHO) at the same position.

5. **Conclude the Answer**:
- Therefore, the essential photosynthetic pigment chlorophyll a has a methyl group at carbon atom 3 of the pyrrole ring II.

### Final Answer:
The essential photosynthetic pigment has a **methyl group** at carbon atom 3 of the pyrrole ring II of chlorophyll a.

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