Chlorophyll a is absent in photosynthetic

Options

A. Bacteria
B. Cyanobacteria
C. Red algae
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding Chlorophyll a**: Chlorophyll a is a green pigment essential for photosynthesis, primarily found in plants, algae, and cyanobacteria. It plays a crucial role in capturing light energy for the process of photosynthesis.

2. **Photosynthesis Process**: In photosynthesis, organisms convert carbon dioxide and water into glucose and oxygen using sunlight. Chlorophyll a is specifically involved in this process, particularly in oxygenic photosynthesis, which occurs in the presence of oxygen.

3. **Absorption Spectrum of Chlorophyll a**: Chlorophyll a absorbs light most effectively in the blue and red wavelengths but reflects green light, which is why plants appear green.

4. **Identifying Organisms Lacking Chlorophyll a**: The question asks about organisms that are photosynthetic but do not contain chlorophyll a. Photosynthetic bacteria, such as purple and green sulfur bacteria, do not have chlorophyll a; instead, they contain a different pigment known as bacteriochlorophyll.

5. **Analyzing the Options**:
- Option 1: Photosynthetic bacteria (correct, as they contain bacteriochlorophyll).
- Option 2: Cyanobacteria (incorrect, as they contain chlorophyll a).
- Option 3: Red algae (incorrect, as they also contain chlorophyll a).
- Option 4: Other photosynthetic organisms (incorrect if they contain chlorophyll a).

6. **Conclusion**: The correct answer is that chlorophyll a is absent in photosynthetic bacteria, which utilize bacteriochlorophyll for photosynthesis.

**Final Answer**: Chlorophyll a is absent in photosynthetic bacteria.

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