The chlorophyll 'a' molecule forms the 'reaction centre' in photosystem

Answer

**Step-by-Step Solution:**

1. **Understanding the Photosystem**: A photosystem is a complex of proteins and pigments that plays a crucial role in the process of photosynthesis. It consists of a reaction center and light-harvesting complexes.

2. **Identifying the Reaction Center**: The reaction center is the part of the photosystem where the primary photochemical reactions occur. It is responsible for converting light energy into chemical energy.

3. **Role of Chlorophyll a**: Chlorophyll a is the primary pigment found in the reaction center of both Photosystem I (PSI) and Photosystem II (PSII). It is essential for capturing light energy.

4. **Excitation of Electrons**: When light is absorbed by chlorophyll a, it excites electrons to a higher energy level. This is a key step in the process of photosynthesis, as these high-energy electrons are then transferred to an electron transport chain.

5. **Conclusion**: Since chlorophyll a is indeed the molecule that forms the reaction center in a photosystem, the statement is correct.

**Final Answer**: The statement "The chlorophyll 'a' molecule forms the 'reaction centre' in photosystem" is correct.

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