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Plants use photosynthesis to convert light energy into chemical energy.

Plants use photosynthesis to convert light energy into chemical energy. In this process, plants produce glucose by using atmospheric carbon dioxide and water in the presence of sunlight. As a result, oxygen is released in the atmosphere as a by-product. Furthermore, the whole photosynthesis process is divided into two broad phases, photochemical and biosynthetic. C3 and C4 pathway, the topic of this article are two ways of biosynthetic process. In a biosynthetic process, plants use water and carbon dioxide to produce carbohydrate.

Also known as the Calvin cycle, Melvin Kelvin first discovered this process. Majority of the plants on the earth uses this process. Furthermore, the first stable product produced by this process is three compound carbon. Hence, the name C3 pathway. Moreover, this cycle occurs in three steps, these are –

C4 pathway of photosynthesis occurs before the C3 pathway. Even though the C3 cycle is found in every plant, the C4 pathway is primarily noticeable in plants of the tropical region. Furthermore, this process is also known as the Hatch and Slack pathway. The first stable product of this process is a four-carbon compound, hence the name. Moreover, there are two C4 cycle steps which every plant follow; these are –

Furthermore, the C4 cycle in plants is useful in hot and arid conditions as plants close their stomata to save water. Before moving forward, here are some C4 cycle notes for a quick recap –

Difference Between C3 and C4 Pathway Some of the key differences between these two pathways are –

The first compound produced in a C3 cycle is a 3-carbon substance named 3-phosphoglyceric acid. On the other hand, in C4 pathways, the primary stable compound is a 4-carbon compound known as oxaloacetate acid.

C3 cycle is found in every plant. But C4 pathway diagram is found primarily in plants of the tropical region.

In the case of C3, it is Ribulose Bi Phosphate (RUBP). For C4, it is phosphoenolpyruvate (PEP).

In C4 plants it is PEP carboxylase and rubisco. However, in the case of C3, it is only rubisco.

Only one carbon fixation occurs in a C3 cycle. In the C4 cycle, double carbon fixation occurs.    

C3 and C4 cycle are two parts of the overall photosynthesis process. More preciously, these are two sections of the biosynthesis process. In this process, plants use water and carbon dioxide to make carbohydrate.

C4 pathway cycle is a part of the biosynthesis process, and it occurs before the C3 period. This process is also known as the Hatch and Slack pathway. The first stable product of this process is a four-carbon compound (oxaloacetate acid), hence the name.

Notably, plants from the tropical region use this process. Owing to lack of water in such harsh conditions, these plants use this process to conserve water.