The Bio-Chemical Phase in Photosynthesis was first discovered by Calvin.

Introduction:
Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy to synthesize organic compounds, primarily glucose. It involves two main phases: the light-dependent reactions and the light-independent reactions (also known as the Calvin cycle or the bio-chemical phase).

Discovery of the Bio-Chemical Phase:
The bio-chemical phase of photosynthesis, also known as the Calvin cycle, was first discovered by Melvin Calvin and his colleagues in the 1940s. Calvin was an American biochemist who conducted groundbreaking research on the pathway of carbon assimilation in plants.

Experimental Setup:
Calvin conducted his experiments using the green alga Chlorella. He exposed the algae to radioactive carbon-14 isotope (14C) to trace the movement of carbon during photosynthesis. By using radioactive carbon, he could track the carbon atoms and determine how they were incorporated into organic molecules.

Key Findings:
Through his experiments, Calvin made several key findings:

1. Carbon Fixation: Calvin discovered that during photosynthesis, carbon dioxide (CO2) from the atmosphere is converted into organic molecules. This process is known as carbon fixation.

2. Enzyme RuBisCO: Calvin identified an enzyme called ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO), which plays a crucial role in the carbon fixation process. It catalyzes the reaction between CO2 and a five-carbon sugar called ribulose-1,5-bisphosphate (RuBP).

3. Formation of PGA: Calvin observed that the initial product of carbon fixation is a three-carbon compound called 3-phosphoglyceric acid (PGA). PGA is formed when CO2 reacts with RuBP.

4. Reduction Phase: Calvin proposed a series of biochemical reactions that convert PGA into glyceraldehyde-3-phosphate (G3P), a three-carbon sugar. This reduction phase requires ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).

5. Regeneration of RuBP: Calvin also discovered that some of the G3P molecules produced are used to regenerate the starting molecule RuBP. This regeneration is essential for the continuous functioning of the Calvin cycle.

Significance:
Calvin's discovery of the bio-chemical phase of photosynthesis provided a detailed understanding of how plants convert carbon dioxide into organic molecules. His research laid the foundation for our current knowledge of the Calvin cycle and its significance in carbon assimilation and the global carbon cycle.

Conclusion:
In conclusion, the bio-chemical phase in photosynthesis, also known as the Calvin cycle, was first discovered by Melvin Calvin. His experiments with radioactive carbon and the green alga Chlorella revealed the mechanisms of carbon fixation, the role of RuBisCO enzyme, and the series of reactions involved in the production of organic molecules. Calvin's findings significantly contributed to our understanding of photosynthesis and its importance in sustaining life on Earth.

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