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What happens during the Calvin-Benson cycle, or dark reaction?
Equation for dark reaction:
#3CO_2# + #6NADPH# + #9ATP to (CH_2O)_3# + #6NADPH# + #9ADP# +# 9#Pi
Diagram of Calvin cycle:
Steps in Calvin Cycle:
1st step: Carbon fixation:
It refers to the initial incorporation of #CO_2# into organic material. We will follow #3# molecules of #CO_2# through the reaction because we want sugars(carbohydrates) as the end product of cycle. And for this, at least 3 molecules of #CO_2# are necessary. Because;#3# molecules of #CO_2#→ 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 #CO_2# molecule is now a part of an organic compound which means carbon has been fixed .
2nd step: Reduction:
In this step, fixed carbon is reduced to energy rich G3P with the energy and reducing power of ATP and NADPH respectively.
Each molecule of PGA recieves an additional phosphate from ATP of light reaction and form 1,3-bisphosphoglycerate.
It is reduced to glyceraldehyde 3-phosphate(G3P) by recieving a pair of electrons donated from NADPH of light reactions.Actually G3P is the carbohydrate that is produced directly from Calvin cycle.
For every #3# molecules of #CO_2# entering the cycle and combining with #3# molecules of RuBp, #6# molecules of G3P are produced. But only #1# molecule of G3P can be counted as a net gain of carbohydrate. Because out of every #6# molecules of G3P formed, only one molecule leaves the cycle to be used by plants for making glucose and other carbohydrates; the other five molecules are recycled to regenerate the three molecules of five carbon RuBP, the #CO_2# acceptor.
3rd step: Regeneration of #CO_2# acceptor, RuBp:
Through a complex series of reactions, the carbon skeletons of five molecules of three-carbon G3P are rearranged into three molecules of five-carbon ribulose phosphate(RuP).
Each RuP is phosphorylated to RuBP. Again #3# molecules of ATP of light reactions are used for this phosphorylation of #3#RuP.
These RuBP are now prepared to recieve #CO_2# again, and the cycle continues.
The Calvin Cycle: Definition, Steps and Products | Earth – The Calvin Cycle, also known as the Calvin-Benson Cycle, refers to the set of light independent redox reactions that takes place in the chloroplasts during photosynthesis and carbon fixation that would convert carbon dioxide into the sugar glucose.Other names for light-independent reactions include the Calvin cycle, the Calvin-Benson cycle, and dark reactions. The most outdated name is dark reactions, which can be misleading because it implies incorrectly that the reaction only occurs at night or is independent of light, which is why most scientists and instructors no longer use it.During Calvin Benson cycle or dark reaction – Option C Carbon dioxide from the air is used to produce glucose and other compounds.This happens during the Calvin-Benson cycle, or dark reaction because the reason is the Calvin cycle is also called as dark reaction or the Benson-Calvin cycle.
8.3B: The Calvin Cycle – Biology LibreTexts – Calvin cycle also known as Calvin-Benson-Bassham or reductive pentose pathway has been the first CO 2 fixation cycle discovered by Calvin, Benson and Bassham in plants and after reported in many other microorganisms [24-26].In this cycle represented in Fig. 18.1, ribulose-1,5-biphosphate carboxylase oxygenase (RuBisCO), a key enzyme of this process, sequesters a CO 2 molecule from theThe Calvin cycle, Calvin-Benson-Bassham (CBB) cycle, reductive pentose phosphate cycle (RPP cycle) or C3 cycle is a series of biochemical redox reactions that take place in the stroma of chloroplast in photosynthetic organisms.. The cycle was discovered in 1950 by Melvin Calvin, James Bassham, and Andrew Benson at the University of California, Berkeley by using the radioactive isotopeDark Reactions. The Calvin-Benson cycle, also called the Calvin cycle, is performed by plants as part of photosynthesis. However, it is known as a dark reaction because, unlike other parts of
What happens during the Calvin-Benson cycle, or dark – • These reactions require three ATP molecules. • RuBP is thus regenerated to begin the cycle again. For the net synthesis of one G3P molecule, the Calvin cycle uses the products of the light reactions: – 9 ATP molecules – 6 NADPH molecules G3P produced by the Calvin cycle is the raw material used to synthesize glucose and other carbohydrates.during Calvin Benson cycle carbon dioxide from the air is used to produce glucose and other compounds. What happens during the calvin-benson cycle or dark reaction? carbon dioxide from the air isBecause in photosynthesis Calvin's cycle is part if the light-independent phase, also called dark phase. it is the stage where light is not required for the process. altimemike altimemike The Calvin cycle can occur in the absence of light.