Multiple Choice
What is the role of NADP+ in photosynthesis?
9. Photosynthesis
Calvin Cycle
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In the Calvin cycle, CO2 is combined with __________.
A
a two-carbon compound to form a three-carbon compound
B
a seven-carbon compound to form two four-carbon compounds
C
a five-carbon compound to form a stable six-carbon compound that can be converted directly to glucose
D
two two-carbon compounds to form a five-carbon compound
E
a five-carbon compound to form an unstable six-carbon compound, which decomposes into two three-carbon compounds
Verified step by step guidance1
Understand the context: The Calvin cycle is a series of biochemical reactions that take place in the chloroplasts of photosynthetic organisms. It is also known as the light-independent reactions or dark reactions.
Identify the key reactants: In the Calvin cycle, carbon dioxide (CO2) is fixed into an organic molecule. The primary molecule that combines with CO2 is ribulose bisphosphate (RuBP), which is a five-carbon compound.
Describe the reaction: CO2 combines with RuBP to form an unstable six-carbon intermediate. This reaction is catalyzed by the enzyme ribulose bisphosphate carboxylase/oxygenase, commonly known as RuBisCO.
Explain the breakdown: The unstable six-carbon compound quickly breaks down into two molecules of 3-phosphoglycerate (3-PGA), which are three-carbon compounds. This is the first stable product of the Calvin cycle.
Summarize the process: The initial step of the Calvin cycle involves the fixation of CO2 into a five-carbon compound (RuBP) to form an unstable six-carbon compound, which then decomposes into two three-carbon compounds (3-PGA). This sets the stage for further reactions that eventually lead to the synthesis of glucose.
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