Final answer:
The instability of the 6-carbon molecule in the Calvin cycle is due to its low activation energy for decomposition, confirmed by chemical synthesis and crystallography. The Calvin cycle uses ATP and NADPH to produce energy-storing molecules and regenerate RuBP. The correct option is B.
Step-by-step explanation:
The 6-carbon molecule generated during the Calvin cycle is extremely unstable because of its low activation energy for decomposition. This molecule is an intermediate that forms when RuBP combines with CO2 and is not stable enough to exist for long before it splits into two molecules of 3-phosphoglycerate (3-PGA).
The existence of this intermediate, though short-lived, was confirmed through chemical synthesis and analysis of its crystal structure.
The Calvin cycle harnesses energy in the form of ATP and NADPH to produce molecules such as Glyceraldehyde-3-phosphate (GA3P), which store the energy captured from photosynthesis. GA3P can then be used to regenerate RuBP or to synthesize glucose and other carbohydrates.
The fixation of atmospheric CO2 during the Calvin cycle is essential for the production of these organic compounds and thus for sustaining life on Earth.