The Calvin cycle is also called as C3 cycle because the first stable product is a three carbon compound, called as phosphoglyceric acid. The Hatch slack cycle is called as C4 cycle because the first stable product is a four carbon compound- oxalo acetic acid.

The First Stable Product of C3 Cycle

The first stable product of the C3 cycle is a three-carbon compound called phosphoglycerate (PGA). PGA is formed after the fixation of CO2 by the enzyme Rubisco and the subsequent cleavage of the six-carbon compound that forms.

Process of Formation

The formation of PGA occurs in the stroma of chloroplasts, and it is the result of the carbon fixation process that occurs during the light-independent reactions of photosynthesis. The C3 cycle begins with the fixation of CO2 by Rubisco, which combines with ribulose-1,5-bisphosphate (RuBP) to form a six-carbon compound. This six-carbon compound is unstable and immediately breaks down into two molecules of PGA.

Importance of PGA

PGA is an important intermediate in the C3 cycle because it serves as the starting point for the synthesis of glucose and other organic molecules. After PGA is formed, it enters a series of reactions that eventually lead to the production of carbohydrate molecules such as glucose, which can be used by the plant for energy or stored for later use.

Conclusion

In summary, PGA is the first stable product of the C3 cycle and is formed as a result of the carbon fixation process that occurs during the light-independent reactions of photosynthesis. PGA is an important intermediate in the synthesis of glucose and other organic molecules and plays a crucial role in the overall process of photosynthesis.