What is the enzymatic basis of this difference

1. Sedoheptulose 1 7-bisphosphate is an intermediate in the Calvin cycle but not in the pentose phosphate pathway. What is the enzymatic basis of this difference?2. . An illuminated suspension of Chlorella is actively carrying out photosynthesis. Suppose that the light is suddenly switched off. How would the levels of 3-phosphoglycerate and ribulose 1 5-bisphosphate change in the next minute?3. An illuminated suspension of Chlorella is actively carrying out photosynthesis in the presence of 1% CO2. The concentration of CO2 is abruptly reduced to 0.003%. What effect would this reduction have on the levels of 3-phosphoglycerate and ribulose 1 5-bisphosphate in the next minute?4. 2-Carboxyarabinitol 1 5-bisphosphate (CABP) has been useful in studies of rubisco.(a) Write the structural formula of CABP.(b) Which catalytic intermediate does it resemble?(c) Predict the effect of CABP on rubisco.