Calvin Cycle (C3 cycle)

The Calvin cycle is also known as the C3 cycle, the nighttime reaction of photosynthesis, or the light-independent reaction. However, it is most active during the daytime when there is a surplus of ATP and NADPH. To build organic molecules, the plant cells use raw materials provided by light reactions.

Stages of Calvin Cycle

There are three stages of the Calvin cycle, 

Carbon fixation: CO₂ binds to RuBP to produce In the necessary procedure known as carbon fixation. Two to three carbon molecules of phosphoglycerate. Ribulose bisphosphate carboxylase/oxygenase, an enzyme with four subunits found in the stroma of chloroplasts, provides the catalyst for this reaction. By digesting roughly three molecules of RuBP per second, this enzyme functions exceedingly slowly. Over 50% of the protein in a normal leaf is RuBisCO. It is believed to be the protein that is most prevalent on earth.

Reduction: It’s Calvin’s cycle’s second phase. The 3-PGA molecules produced by carbon fixation are changed into glucose molecules, which are simple sugar molecules. ATP and NADPH produced during the photosynthesis’ light-dependent processes provide energy for this stage. Thus, the Calvin cycle becomes a process through which plants transform solar energy into molecules that can be stored for a long time, like sugars. The sugars receive the energy from the ATP and NADPH. Since electrons are transferred to 3-PGA molecules to create glyceraldehyde-3 phosphate, this process is known as reduction.

Regeneration: The Calvin cycle’s third stage is a difficult procedure that needs ATP. While others are recycled to regenerate the RuBP acceptor at this stage, some of the G3P molecules are utilized to create glucose.

Equation & Products of Calvin Cycle

6 NADPH + 9 ATP + 3CO₂ + 5H₂O —-> G3P + 2H⁺ + 6NADP⁺ + 9ADP + 8Pi

(G3P – Glyceraldehyde-3 phosphate ; Pi= Inorganic phosphate)

The process by which plants convert carbon dioxide, water, and sunlight into oxygen and energy in the form of sugar is known as photosynthesis. Autotrophic plants produce their own food through a process called photosynthesis. Sunlight, chlorophyll, CO2, and water are four crucial components needed for this process. The two steps of photosynthesis are the Light Reaction and the Dark Reaction.