Which is a contribution of Melvin Calvin

Answer

**Step-by-Step Solution:**

1. **Introduction to Melvin Calvin**: Melvin Calvin was a prominent biochemist known for his work on the process of photosynthesis.

2. **Use of Radioisotope Methodology**: He utilized radioactive isotopes, specifically Carbon-14 (C-14), as a tracer to study the fixation of carbon dioxide during photosynthesis.

3. **Investigation of the Calvin Cycle**: Through his experiments, Calvin investigated the series of biochemical reactions that occur during photosynthesis, which are now known as the Calvin Cycle.

4. **Discovery of the First Product**: Calvin discovered that the first stable product of carbon dioxide fixation in photosynthesis is 3-phosphoglyceric acid (PGA).

5. **Identification of the Pathway**: He identified that the Calvin Cycle produces a 3-carbon organic acid, which is why it is referred to as the C3 pathway. This is because the first stable product formed during the cycle contains three carbon atoms.

6. **Applicability to Different Plants**: The Calvin Cycle occurs in all photosynthetic plants, including both C3 and C4 plants, indicating its fundamental role in the process of photosynthesis.

7. **Conclusion**: Melvin Calvin's contributions significantly advanced our understanding of photosynthesis and the biochemical pathways involved, leading to the naming of the Calvin Cycle in his honor.

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