Figure 8.2
-To identify the molecule that accepts CO₂, Calvin and Benson manipulated the carbon-fixation cycle by either cutting off CO₂ or cutting off light from cultures of photosynthetic algae. They then measured the concentrations of various metabolites immediately following the manipulation. How would these experiments help identify the CO₂ acceptor? Study Figure 8.2 to help you in determining the correct answer.

Question

Quizplus · Accepted Answer

If the CO₂ acceptor is being identified, then the concentration of the acceptor would change when CO₂ is cut off or when light is cut off. When CO₂ is cut off, the Calvin cycle can’t proceed and the metabolites accumulate leading to an increase in their concentration. This means that the concentration of the CO₂ acceptor would also increase because it can’t be consumed. When light is cut off, the reactions of the Calvin cycle depending on light can’t proceed. This would lead to both the metabolites and the CO₂ acceptor concentration decreasing. Therefore, the CO₂ acceptor concentration would increase when CO₂ is cut off, but decrease when the light is cut off.

Figure 8.2 -To Identify the Molecule That Accepts CO₂, Calvin and Benson