To Identify the Molecule That Accepts CO₂, Calvin and Benson

Multiple Choice

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 the figure above to help you in determining the correct answer.

A) The CO₂ acceptor concentration would decrease when either the CO₂ or light are cut off.
B) The CO₂ acceptor concentration would increase when either the CO₂ or light are cut off.
C) The CO₂ acceptor concentration would increase when the CO₂ is cut off, but decrease when the light is cut off.
D) The CO₂ acceptor concentration would decrease when the CO₂ is cut off, but increase when the light is cut off.
E) The CO₂ acceptor concentration would stay the same regardless of the CO₂ or light.