Describe C3 Pathway

The metabolic route followed by most temperate plants during the light-independent phase of photosynthesis, with the three-carbon molecule glycerate 3-phosphate as the initial product. This is created when carbon dioxide reacts with ribulose bisphosphate in the Calvin cycle’s initial step. C3 plants are those that follow this metabolic route. Photorespiration has unfavourable consequences for plants that rely entirely on the C3 pathway for carbon fixation, such as wasteful CO2 loss. Drought, high temperatures, and low nitrogen or CO2 concentrations all cause photorespiration.

Describe C3 Pathway

Now we will learn more about pathway C3 pathway, the first stable intermediate compound formed in the C3 pathway and at last in the C3 pathway diagram.

Pathway

Firstly, We Will Take a Look at What We Mean by Carbon Fixation

Carbon fixation is the process of adding carbon dioxide to organic molecules (typically carbohydrates) in order to prevent it from staying in a free state in the atmosphere. As a result, energy is generated. CO2 assimilation is another name for carbon dioxide fixing or we can say Carbon fixation is the process through which photosynthetic organisms (such as plants) convert inorganic carbon into organic molecules (carbohydrates). CO2 fixation, for example, is a kind of carbon fixation in which atmospheric carbon dioxide is turned into carbohydrates. It is, in fact, the Calvin Cycle’s first crucial phase. When it comes to the process of photosynthesis, carbon fixation is crucial. Photosynthesis would not be possible without carbon fixation in the Calvin cycle, and plants would be unable to produce their own food.

Coming on to Pathway

Carbon may be repaired in two ways, autotrophic and non-autotrophic. There are six (6) primary autotrophic paths that the carbon may choose from, according to what has been revealed. Carbon fixation in the chloroplasts of plants and the cells of cyanobacteria are examples of autotrophic carbon fixation mechanisms. The remaining five routes are found in two bacteria, two archaea, and one that is found in both bacteria and archaea.

C3 Pathway

The C3 carbon fixation pathway is the Calvin cycle’s first step. It begins with the enzyme rubisco catalysing the carboxylation of Ribulose-1,5-bisphosphate by CO2, resulting in the highly unstable 6-carbon intermediate 3-keto-2-carboxyarabinitol 1,5-bisphosphate, which splits instantly into two molecules of the more stable 3-phosphoglycerate, an organic compound with three carbon atoms (hence the name C3).

Photorespiration has unfavourable consequences for plants that rely entirely on the C3 pathway for carbon fixation, such as wasteful CO2 loss. Drought, high temperatures, and low nitrogen or CO2 concentrations all cause photorespiration. In order to avoid excessive water loss, the stomata shut under these circumstances. Closing stomata raises O2 levels, and the enzyme rubisco interacts with O2 rather than CO2, resulting in CO2 loss rather than fixation.

The First Stable Intermediate Compound Formed in C3 Pathway

A three-carbon molecule is the first stable intermediate of carbon dioxide reduction. As a result, the C3 cycle is named after this method of carbon reduction. RuBisCO, which carboxylates Ribulose- 1,5 bisphosphate (RUBP) into phosphoglyceric acid, causes the first carboxylation in the C3 cycle. Later on, the phosphoglyceric acid is converted to phosphoglyceraldehyde, which is utilised to make carbohydrates and recycle RUBP.

C3 Pathway Diagram

The C3 pathway is named after the first molecule generated in the cycle, 3-phosphoglyceric acid (a 3-carbon molecule). The Calvin Cycle is used by around 85 percent of all plants on Earth to fix carbon. During the one-step process, the enzyme RuBisCO (ribulose bisphosphate carboxylase/oxygenase) begins an oxidation reaction, resulting in part of the energy utilised in photosynthesis to be lost via a process known as photorespiration. 

Cowpea, cassava, soybean, spinach, peanuts, cotton, wheat, barley, most trees and grasses are examples of C3 plant species and they are among the world’s most significant sources of calories. These crops might benefit from the energy-saving processes of C4 photosynthesis since the places where they are produced are often hot and dry. While C3 photosynthesis has greater potential for development, our computer simulations indicate that both forms of photosynthesis may be improved to maximise crop productivity.

As a consequence, the quantity of carbon fixed by the plant and released back into the environment as carbon dioxide is reduced by around 25%.