The Calvin cycle begins when a molecule of CO₂ reacts with a highly reactive phosphorylated five-carbon sugar named:
Correct answer: A. Ribulose bisphosphate
- A. Ribulose bisphosphate
- B. Fructose-1,6-bisphosphate
- C. Glucose-6-phosphate
- D. Glyceraldehyde-3-phosphate
Explanation
The Calvin cycle begins when carbon dioxide reacts with ribulose-1,5-bisphosphate, a five-carbon compound that serves as the starting point of the cycle. This reaction is driven by the enzyme Rubisco, which attaches carbon dioxide to the molecule, forming two molecules of 3-phosphoglycerate. This step is known as carbon fixation and marks the entry of inorganic carbon into an organic form that plants can use to build sugars. Without ribulose-1,5-bisphosphate, the Calvin cycle could not continue, as it plays a key role in capturing carbon dioxide and maintaining the cycle's flow.
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Cellular respiration explains how cells release energy from glucose through glycolysis, the link reaction, Krebs cycle and electron transport chain. It includes ATP production, substrate-level and oxidative phosphorylation, aerobic versus anaerobic respiration, and the roles of mitochondria, oxygen and fermentation in energy transfer.
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More Bioenergetics questions
First phase of Calvin cycle is:
The cyclic series of reactions by which the carbon is fixed and reduced, resulting in the synthesis of sugar, is called:
The details of the path of carbon in the dark reaction of photosynthesis were discovered by Melvin Calvin and his colleagues at:
During the first step of the reduction phase of the Calvin cycle, the following change occurs:
The assimilatory and reducing powers synthesized in the light reaction of photosynthesis are utilized in:
The phase of the Calvin cycle in which fewer ATPs of the light reaction are used is: