Multiple choice Which of the following molecules acts as primary acceptor of CO2 in photosynthesis? Oxaloacetic acid 3-phosphoglyceric acid Ribulose bisphosphate Pyruvic acid Triose phosphate Reveal answer Fill a bubble to check yourself C Correct answer Explanation The acceptor molecule of CO2 is a 5-carbon ketose sugar – Ribulose bisphosphate (RuBP) which gets converted to two molecules of 3-phosphoglyceric acid in presence of RuBP carboxylase-oxygenase.