Chapter 13: Photosynthesis in Higher Plants

Rubisco and PEP case are the two important enzymes of C3 and C4 pathways. Rubisco is the primary CO₂ receiver in C3 facilities while PEP case is the main CO₂ receiver for C4 facilities. The important enzyme of the C3 pathway is RUBisCO and C4 is PEPcase. In the Calvin cycle, carboxylation is the most crucial step. Carbon dioxide is utilized for the carboxylation of RuBP. This is catalyzed by RuBP carboxylase which results in the formation of two molecules of 3-PGA. The primary carbon dioxide acceptor in the C4 pathway is 3 carbon molecule phosphoenolpyruvate.

The enzyme catalyzes during the Calvin cycle to transform carbon dioxide into sugar. From cyanobacteria to the floors of large trees; literally, Rubisco is present all over the place. All carbon in the biosphere can be said to be derived from Rubisco carbon fixation. Therefore it is considered as the world’s largest enzyme.

Photorespiration does not occur in C4 plants because they increase the concentration of carbon dioxide at the enzyme site by a mechanism. This happens when the C4 acid from the mesophyll is broken down in the bundle sheath cells to release Carbon dioxide which further results in the increasing the intracellular of carbon dioxide. The high carbon dioxide concentration in the plants makes all Rubisco bind to carbon dioxide and no oxygen-binding exists.

Photosynthesis in higher plants is the main process by which plants create the essential nutrients for their growth. In this method, plants utilise the energy emitted from the sunlight and convert carbon dioxide into essential molecules needed for growth. Different molecules utilised are enzymes, sugars and chlorophyll, which are important for the growth of plants.