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The second stage of photosynthesis, which takes place in the stroma of the chloroplast, can occur without the presence of sunlight. In this stage, known as the Calvin Cycle, carbon molecules from CO2 are fixed into glucose (C6H12O2). The reactions of the Calvin Cycle is as follows:

1. A five-carbon sugar molecule called ribulose bisphosphate, or RuBP, is the acceptor that binds CO2 dissolved in the stroma. This process, called CO2 fixation, is catalyzed by the enzyme RuBP carboxylase, forming an unstable six-carbon molecule. This molecule quickly breaks down to give two molecules of the three-carbon 3-phosphoglycerate (3PG), also called phosphoglyceric acid (PGA).

2. The two 3PG molecules are converted into glyceraldehyde 3-phosphate (G3P, a.k.a. phosphoglyceraldehyde, PGAL) molecules, a three-carbon sugar phosphate, by adding a high-energy phosphate group from ATP, then breaking the phosphate bond and adding hydrogen from NADPH + H+.

Three turns of the cycle, using three molecules of CO2, produces six molecules of G3P. However, only one of the six molecules exits the cycle as an output, while the remaining five enter a complex process that regenerates more RuBP to continue the cycle. Two molecules of G3P, produced by a total of six turns of the cycle, combine to form one molecule of glucose.

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Related Questions

The enzymes for the light dependent reactions are found in the thylakoid membrane while the Calvin cycle happens in the what?

The Calvin cycle happens in the stroma of the chloroplast.


Where in the plant chloroplast does each stage happen?

The light reaction happens in the thylakoid membrane and converts light energy to chemical energy.The dark reaction takes place in the stroma within the chloroplast, and converts CO2 to sugar.


Where are sugar synthesized in the chloroplast?

It happens in stroma.Dark reaction makes sugar.


How does C02 travel around the world?

CO2 is in the air and as the air moves so does the CO2 in it.


Were does the Calvin cycle take place in?

The Calvin cycle takes place in the stroma of chloroplasts.


Which part of the chloroplast is associated with the production of glucose?

The production of glucose takes place during the light independent reactions (Calvin cycle) in the stroma of the chloroplast.


What is the fluid in the chloroplasts?

Stroma


Sugars are built where?

In the stroma


What is fibromyxoid stroma?

fibromyxoid stroma


Where does the dark reaction take place?

It takes place in the stoma


What are the spaces between the grana in chloroplast called?

They are called stroma.


What gases are given off and taken by the plant through the stroma?

Through the stroma, plants primarily exchange carbon dioxide (CO2) and oxygen (O2). During photosynthesis, plants take in carbon dioxide from the atmosphere and release oxygen as a byproduct. This gas exchange occurs in tiny openings called stomata, which are often located on the underside of leaves. Overall, plants absorb CO2 for photosynthesis and release O2 into the environment.