Chlorophyll a and b have the same structure except that Chla has `"_____________"` group while Chl b has group in side chain.

Explanation

To answer the question regarding the structural difference between chlorophyll a and chlorophyll b, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Chlorophyll Structure**: Both chlorophyll a and b are essential pigments in higher plants that play a crucial role in photosynthesis. They have a similar basic structure but differ in their side chains.

2. **Identifying the Key Difference**: The primary difference between chlorophyll a and b lies in their side chains. Specifically, chlorophyll a contains a specific group in its structure that distinguishes it from chlorophyll b.

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