Consider the situation where photosynthesis is going on at a steady pace in a typical experiment with a light on, and carbon dioxide is being combined with ribulose-bisphosphate (RuBP) to produce 3-phosphoglycerate (3PG). Then suddenly the source of carbon dioxide is eliminated. What changes in the concentrations of 3PG and RuBP would occur?
1. 3PG levels rise, RuBP levels fall.
2. 3PG levels fall, RuBP levels rise.
3. 3PG levels rise, RuBP levels rise.
4. 3PG levels fall, RuBP levels fall.