Question

The primary acceptor of carbon dioxide in C${}_3$ plants is a

• A. 2 carbon compound
• B. 6 carbon compound
• C. 5 carbon compound
• D. 3 carbon compound

Answer 1

The correct option is C 5 carbon compound

During the biosynthetic phase of photosynthesis, glucose is synthesised. This starts with the CO${}_2$ fixation. Carbon dioxide enters the chloroplast through stomata and combines with RuBP present in the stroma of chloroplast. Hence, the primary acceptor of CO${}_2$ is RuBP (ribulose-1,5-bisphosphate). It is a 5 carbon compound.

RuBP combines with one molecule of $C{O}_2$ and forms an unstable 6 carbon compound that splits into two molecules of 3-PGA. Hence, PGA is the first stable product formed during light independent reactions of photosynthesis. PGA is a 3 carbon compound. Hence, these plants are called C${}_3$ plants.