To Identify the Molecule That First Reacts with CO₂ in the Light-Independent

Multiple Choice

To identify the molecule that first reacts with CO₂ in the light-independent reactions of photosynthesis, Calvin and Benson manipulated the carbon-fixation cycle by either elminating CO₂ or light from cultures of photosynthetic algae. Which of the following statements best predicts the immediate effects of these manipulations on the concentration of the molecule that initially reacts with CO₂?

A) The concentration would decrease when either the CO₂ or light is eliminated.
B) The concentration would increase when either the CO₂ or light is eliminated.
C) The concentration would decrease when the CO₂ is eliminated, but increase when the light is eliminated.
D) The concentration would increase when the CO₂ is eliminated, but decrease when the light is eliminated.