What is the first step of the Calvin-Benson cycle?

1 Answer
Saliha
Dec 18, 2017

Carbonfixation

Explanation:

It refers to the initial incorporation of CO2 into organic material. We will follow 3 molecules of CO2 through the reaction because we want sugars(carbohydrates) as the end product of cycle. And for this, at least 3 molecules of CO2 are necessary.

Because;
3 molecules of CO2→ contain 3 C→ so at least they will give 1 carbohydrate molecule( a triose).

  • Calvin cycle begins by the reaction of CO2 with highly reactive phosphorylated five carbon-sugar named ribulose bisphosphate(RuBP).
  • This reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase also known as Rubisco.
  • The product of this reaction is highly unstable six-carbon intermediate that immediately breaks into two molecules of three-carbon-compound named 3-phosphoglycerate(PGA).
  • The carbon that was originally a part of CO2 molecule is now a part of an organic compound which means carbon has been fixed.
    enter image source here

https://www.khanacademy.org/science/biology/photosynthesis-in-plants/the-calvin-cycle-reactions/a/calvin-cycle

Note:
Rubisco is the most abundant protein in the chloroplast and probably the most abundant protein on Earth.

Related questions
See all questions in Photosynthesis
Impact of this question
5144 views around the world
You can reuse this answer
Creative Commons License