Calvin’s cycle is the second part of photosynthesis. The main function of the Calvin cycle is Manufacture sugar. The phases of the Calvin cycle are: carbon fixation, reduction and regeneration.
Plants have the ability to produce organic molecules from inorganic molecules, and for this a series of specialized processes come into play, and one of them is the so-called Calvin cycle, Calvin-Benson cycle or cycle of carbon fixation cycle of photosynthesis. In this ecology article, we explain What is the Calvin cycle, its phases, function and importanceso that you can easily understand what this important process that occurs in plants is.
What is the Calvin cycle and where it happens
Calvin’s cycle is also called Calvin-Benson cycle or carbon fixation cycle of photosynthesis. It is a Biochemical Processes Series that occur in plants. Specifically happens in space Interior of chloroplastscalled estromas, which in turn are inside the leaves.
It’s a Anabolic type cyclebecause I know manufactures sugar from smaller and simple. In addition, it consumes energy and does not produce it. It happens during the day and night, but it is independent of the light.
Calvin cycle phases
- Carbon fixation: The outer CO2 of carbon enters through the stoma of the leaves into the cell to the stomination of the chloroplast, to combine with an acceptor molecule called Rubp that has 5 carbons. This results in 6 carbons, which will be catalyzed by the Rubisco enzyme to divide into 3 carbon molecules called 3-PGA, which means 3-phosphoglyceric acid. Here you can read more about the carbon cycle: what it is, how it works and its importance.
- Reduction: Here, the 3-PGA molecules will be converted into sugar molecules called G3P or glyceraldehyde-3-phosphate, with the help of the ATP as a source of chemical energy, and NADPH as a reducing power that donates electrons that have a lot of energy.
- Regeneration: Here the cycle closes, and some G3P will return to train Rubp, and others will form sugar, which is the final result of the Calvin cycle. This is done through ATP.
These are the phases of the Calvin cycle or Calvin-Benson cycle, but it must be considered that the cycle does not end here and it is necessary to occur several times to be able to manufacture the sufficient amount of molecules.
This cycle must be completed 3 times for 3 CO2 molecules to be fixed And there is a G3P or sugar molecule.
Although the Calvin cycle is photo independent, it is important to mention that the NADPH and the ATP that they use come from photophosphorylation, a process that does need light. For this reason, the Calvin cycle is indirectly influenced by light, and there are some components, such as Rubisco and certain enzymes, which are modified not directly by the influence of light.
Calvin cycle function
The function of the Calvin cycle is Synthesize sugar production and regenerate certain molecules that they serve again from CO2 acceptors and that the cycle can continue to be repeated. To summarize the function and the process, we can say that CO2 enters the plant and comes out in the form of sugar.
Regarding the purpose of the molecules produced, glucose that is obtained from the Calvin cycle is used by the plant to manufacture indispensable compounds for its development and structure, from the carbons that make it up. Such compounds to be formed from carbon are Lipids, amino acids and nucleic acids.
Now, plants can be classified according to the number of carbons that the first product of the Calvin cycle has. Thus, most plants are C3. These close their stomata when there are very warm days to avoid perspiring so much, but since the CO2 that enters is also lower, the sugar that occurs is also. Warm places plants such as tropical, corn or cane, do not slow down their photosynthesis despite closing the stomata, and do not foTorespir. Thus, they have as a product a compound of 4 carbons called oxalacetate. The Calvin cycle here is the same, but they have two different enzymes that cause the most efficient 4 carbons sugar at low levels. These plants are known as C4.
Another function of the Calvin cycle is carbon fixation from CO2that is, they leave it bioavailable for other organisms to integrate it. Hence the importance of the cycle for the entire planet.
Importance of the Calvin cycle
The Calvin cycle is not only Important for plants by the aforementioned functions, but also of indispensable importance for the rest of life forms, because they are The base of the food chain.
Calvin cycle products are incorporated by heterotrophic animalsalso called primary consumers, or for simpler, herbivorous animals. The carbon that exists in living beings that do not produce their own food comes from the carbon transfer initiated from the Calvin cycle.
Living beings or heterotrophic organisms take energy from plants to survive and be able to form all the blocks that form their body. Some animals can directly take the energy of the plants, but others can do it by the transfer through the food chain. The latter are secondary consumers and tertiary consumers who feed on other animals, but it is important to remember that carbon had its origin in plants.
Heterotrophic organisms are also important to the Calvin cyclebecause they They release CO2 necessary to obtain carbon for sugar. Thus, the food chain or trophic chain closes in a functional cycle where everything is integrated again.
Now that you know better what the Calvin cycle is, we recommend you review photosynthesis: what is, phases and importance.
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- Tortora, G., Funke, B. & Case, C. (2007) Introduction to microbiology. Argentina: Pan -American Medical Editorial.
- Sadava, D. & Purves, W. (2008) Life, the science of biology. Argentina: Pan -American Medical Editorial.
