C4 pathway or the Hatch-Slack pathway is one of the methods of carbon fixation.
The process of carbon fixation takes place in the mesophyll cells wherein a carbon dioxide molecule is attached to phosphoenolpyruvate (PEP), a three-carbon compound, by the PEP carboxylase enzyme to form a four-carbon compound called oxalacetate; hence, the name of the pathway is the C4 pathway.
The oxaloacetate converts into malate that is transported to the bundle sheath cells.
The malate undergoes decarboxylation to produce carbon dioxide and pyruvate.
The carbon dioxide molecule binds to rubisco to enter the Calvin cycle.
The pyruvate returns to the mesophyll cells to bind with ATP to form PEP.
The advantage of C4 plants is that the carbon dioxide fixation and Calvin cycle take place in different parts of the leaf which minimizes photorespiration and efficiently fixes carbon dioxide.
C4 plants are usually found in hot regions.
Examples of C4 plants are corn, sorghum, and sugarcane.
The C4 pathway is shown in the illustration below:
