Calvin Cycle Process: Step by Step Facts And Diagram

by

Many complex reactions are needed in order to survive. Yes, many reactions and mechanisms have been processed in each cell of every living organism to sustain on this planet.

The Calvin cycle process calvin cycle steps is a mechanism that happens only in the photosynthetic organism. The Calvin cycle process is a major and complex process in the photosynthetic organism as it aids in the production of the carbohydrate molecule which is the basic energy source of the organism. 

Photosynthesis is a process in which the organism that are capable of photosynthesis or the photosynthetic organism  makes ready of their fuel for survival.

The photosynthesis process takes place in 2 steps.

The light dependent reaction involves light from the sun- solar energy to produce NADPH  and ATP molecules.

ADP + NADP + H2O → ATP +NADPH + H ion + O2

The light independent reactions do not involve light, that is they happen in the absence of light in which the NADPH– nicotinamide adenine dinucleotide phosphate and ATP– Adenosine triphosphate from the light dependent process is utilized along with the atmospheric carbon- di-oxide to form carbohydrate molecule- Glucose.

calvin cycle process calvin cycle steps
Stoma- Chloroplast
Image Credits- Flickr

ATP + NADPH + CO2 → ADP + NADP + Glucose

The Calvin cycle process is a sequence of processes that happens post light dependent reaction.

light independent reaction example
Photosynthesis
Image Credits- Pixabay

What are the Calvin cycle process Calvin cycle steps?

The Calvin cycle is also called a light independent reaction as it does not involve any light source.

There are 3 phases/ stages in Calvin cycle

Read More on Sequence Of Nitrogenous Bases In RNA: What, Why, Purpose, Detailed Facts

Calvin cycle diagram:

Simplified photorespiration diagram
Calvin cycle diagram
Image credits- Wikimedia

Calvin cycle equation:

The overall calvin cycle chemical equation is:

3 CO2 + 6 NADPH + 5 H2O + 9 ATP → glyceraldehyde-3-phosphate (G3P) + 2 H+ + 6 NADP+ + 9 ADP + 8 Pi (where Pi is inorganic phosphate)

Explanation of the equation:

  • The carbon- di-oxide molecule in the atmosphere will be captured- CO2
  • The end output of light dependent reaction of photosynthesis – NADPH- nicotinamide adenine dinucleotide phosphate and ATP
  • Along with the water that is present in the soil/ ground – H2o
  • Glyceraldehyde-3-phosphate or G3P, Hydrogen ion or H, Nicotinamide adenine dinucleotide phosphate or NADP, Adenosine di-phosphate or ADP and Pi which is the phosphate.

Read More on Are Bacteria Prokaryotic Or Eukaryotic: Why, How And Detailed Insights And Facts

Carbohydrate formation in Calvin cycle:

Phase- I – Carbon Fixation:

  • In the phase-1 that is carbon fixation, a carbon-di-oxide or the CO2 molecule from the atmosphere merges or linkes itself with a 5-C or 5-carbon acceptor molecule which is called the ribulose-1,5-bisphosphate or shortly known as RuBP.
  • So now 1c or 1 carbon from the carbon dioxide merges with the 5C or 5 Carbon acceptor molecule, the ribulose-1,5-bisphosphate and the product is a 6C or 6 carbon atom.
  • The six-carbon compound is then broken into 2 molecules, 3 carbon compounds each which is called the 3-phosphoglyceric acid or 3-PGA.
  • This reaction is accelerated by the enzyme RuBP carboxylase/oxygenase, also known as RuBisCO which is also a catalyst in this reaction. 
  • RuBisCo plays a vital role in the photosynthesis process and noted to be one of the abundant enzyme on earth.
4388295140 bd8f0dfa2f z
Carbon fixation
Image Credits- Flickr

Read More on Difference between animal and plant cell chromosomes: Comparative analysis on structure, function and facts

Reduction in Calvin cycle

Phase- II – Reduction:

  • The second phase of the Calvin cycle involves the reduction process.
  • Here the 3-PGA molecules that has come from the carbon fixation process are then transformed or broken down into smaller molecules of a simple sugar called the  glyceraldehyde-3 phosphate (G3P).
  • 3-PGA – glyceraldehyde-3 phosphate (G3P)
  • Further this reaction uses energy from ATP-Adenosine triphosphate and NADPH (nicotinamide adenine dinucleotide phosphate) produced from the light-dependent reactions of photosynthesis. The molecules that are obtained from the solar energy are converted into simple sugars here for storage.
  • This stage is known as “reduction” process as the NADPH (nicotinamide adenine dinucleotide phosphate) molecule gifts electrons to the 3-phosphoglyceric acid molecules to combine and formulate glyceraldehyde-3 phosphate
  • Note: In chemistry, the process of donating electrons is called “reduction,” while the process of taking or gaining electrons is called “oxidation.”
4387534029 3f8fd982c5 c
Carbon reduction
Image Credits- Flickr

Read More on Why chromosomes are in pairs: comparative analysis on structure, function and facts.

Calvin cycle products

Phase- III- Regeneration of Ribose 

  • Few glyceraldehyde-3 phosphate molecules are assigned to make glucose, while the rest should be recycled to revitalize the five-carbon RuBP compound that is used to accept new carbon molecules in the phase- I.
  • The regeneration process needs ATP. It is a tedious mechanism involving multiple steps.
  • As it takes six carbon molecules to produce or build up a glucose molecule, this flow must be duplicated or redo six times in cycle to make one single molecule of glucose.
  • To succeed and result in the flow of process in this equation 5 out of six,  glyceraldehyde-3 phosphate molecules that are fabricated through the Calvin cycle are regenerated or renewed to form RuBP molecules. 
  • The sixth leaves the reaction or the cycle to aim for one half of a glucose molecule.

Read More on Is Cyanobacteria Unicellular Or Multicellular: Why, How And Detailed Insights

Frequently Asked Question on Calvin cycle process and Calvin cycle steps:

The Calvin cycle is known as a dark reaction, so what- Does this happen at night?

The Calvin cycle has many names like light independent process, calvin benson cycle or dark reaction of photosynthesis.

No, the calvin cycle does not happen at night. It just does not use light energy for further product generation that doesn’t mean it happens at night.

The calvin cycle takes place in the stromal region of the chloroplasts organelle.

What is the end product of the Calvin cycle?

Glucose is the end product of the Calvin cycle

Also Read: