Q4. Sucrose has 12 carbon atoms. Using NCERT’s figures per CO, how many turns of the Calvin cycle, ATP and NADPH would the carbon of one sucrose need?
12 CO, so 12 turns; ATP = 12 × 3 = 36; NADPH = 12 × 2 = 24 (per-CO figures from NCERT page 145; this ignores the extra energy used in joining the sugars, which is beyond the NCERT text).
Q5. Which isotope did Calvin use, and what was the first product of CO fixation he found?
Radioactive C; the 3-carbon 3-phosphoglyceric acid, PGA (NCERT page 142).
Q6. What happens to the biosynthetic phase immediately after light becomes unavailable?
It continues for some time and then stops; it starts again when light is made available (NCERT page 142).