What is the primary carboxylation product formed when RuBisCO fixes carbon dioxide in C3 plants?
Answer and explanation
Correct answer: B. 3-Phosphoglyceric acid (3-PGA)
- Step 1: RuBisCO catalyzes the addition of to the 5-carbon acceptor ribulose 1,5-bisphosphate (RuBP).
- Step 2: This yields a transient, unstable 6-carbon branched intermediate (2-carboxy-3-keto-D-arabinitol 1,5-bisphosphate).
- Step 3: The intermediate immediately undergoes hydrolytic cleavage to form two molecules of 3-phosphoglyceric acid (3-PGA), a 3-carbon compound.
Answer
3-Phosphoglyceric acid (3-PGA)
Why not the others: 'Oxaloacetic acid (OAA)' is the 4-carbon primary carboxylation product in C4 and CAM plants, catalyzed by PEP carboxylase; 'Phosphoenolpyruvate (PEP)' is the primary acceptor in C4 plants, not a product; 'Glyceraldehyde 3-phosphate (G3P)' is formed in the subsequent reduction phase of the Calvin cycle requiring ATP and NADPH.
Practise more Photosynthesis in Higher Plants.
Free questions with an explanation for every one, and full timed NEET UG mock tests.
More Photosynthesis in Higher Plants questions
- Which structural compartment within the chloroplast is the specific site for the light-independent enzymatic reactions (Calvin cycle) of pho…
- In T.W. Engelmann's classic experiment using the green alga Cladophora and aerobic bacteria, the bacteria accumulated primarily in regions…
- During non-cyclic photophosphorylation, what is the primary role of the oxygen-evolving complex (OEC) associated with Photosystem II?
- Which essential inorganic ions are required as catalytic cofactors for the photolysis of water in Photosystem II?
- In the Z-scheme of non-cyclic electron transport, what is the immediate electron acceptor that accepts excited electrons from the reaction c…
- Which of the following conditions favors cyclic photophosphorylation over non-cyclic photophosphorylation in plant chloroplasts?