Calvin cycle


Also found in: Dictionary, Encyclopedia, Wikipedia.
Calvin cycleclick for a larger image
Fig. 86 Calvin cycle . The ‘dark’ reactions of the Calvin cycle.

Calvin cycle

a series of chemical reactions, first described by Melvin CALVIN, which take place in the watery matrix of CHLOROPLASTS, where carbon dioxide is incorporated into more complex molecules and eventually carbohydrate. Energy for the reactions is supplied by ATP with NADPH (see NADP acting as a reducing agent, both having been produced in the light reactions of PHOTOSYNTHESIS. Since light is not required for the Calvin cycle to continue (provided CO2 ,ATP and NADPH are present) the steps are called the ‘dark’ reactions.

Every turn of the cycle fixes one molecule of carbon dioxide by producing two molecules of PGA and then two molecules of PGAL; three turns are necessary to release one molecule of PGAL (C3) for the glucose pathway with the remaining five PGAL molecules remaining within the cycle. Thus six turns produce sufficient quantities of PGAL for the production of one molecule of glucose (C3 + C3 = C6).

Calvin cycle

see dark reaction.
References in periodicals archive ?
Following the musical, there is a quick review of the major steps of the Calvin cycle and their relation to internal anatomy of the leaf and the photochemical reactions in the thylakoids.
Why is it important for the plant to use some of the 3-carbon aldehyde (glyceraldehyde-3-phosphate) that is produced in the Calvin cycle to make more 5-carbon RuBP (Ribulose-1,5-bisphosphate)?
This question requires students to think of the overall picture of photosynthesis, and their knowledge of both the Calvin cycle and the photochemical reactions.
I compared the performance of the students who had learned about the Calvin cycle through the standard methods of review with textbook diagrams when I did not use this musical in my classes (a total of 111 students from six classes) to those who had been additionally exposed to this in-class activity (a total of 22 students from one class).