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, chlorophyll a, we need to analyze the structure of chlorophyll a and identify the group present at carbon atom 3 of the pyrrole ring II.

### Step-by-Step Solution:

1. **Identify Chlorophyll a Structure**:
- Chlorophyll a is a vital pigment in photosynthesis, and its chemical formula is C55H72O5N4Mg. It contains a complex structure that includes a porphyrin ring system.

2. **Understand the Pyrrole Ring**:
- Chlorophyll a contains four pyrrole rings, which are cyclic structures made up of nitrogen and carbon atoms. Each pyrrole ring contributes to the overall structure of chlorophyll.

3. **Locate Carbon Atom 3 in Pyrrole Ring II**:
- In the context of the pyrrole rings, carbon atoms are numbered. We need to focus on pyrrole ring II and specifically look at carbon atom 3.

4. **Identify the Group at Carbon Atom 3**:
- In chlorophyll a, at carbon atom 3 of pyrrole ring II, there is a methyl group (-CH3) attached. This is a significant characteristic of chlorophyll a.

5. **Conclusion**:
- 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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