Question

$C{O}_2$ acceptor in $C_3$ cycle is

• A. Oxalo acetic acid
• B. Ribulose- 1, 5- bisphosphate
• C. Phospho enol pyruvate
• D. Malic acid

Answer 1

Answer: (B)

Ribulose- 1, 5- bisphosphate

PEP carboxylase catalyzes carboxylation of phosphoenolpyruvate (PEP, the primary acceptor of $C{O}_2$) to form four carbon compound oxaloacetate in mesophyll cells of $C_4$ plants. OAA is converted into malic acid which enters bundle sheath cells and undergoes decarboxylation. In $C_3$ cycle, RUBISCO catalyzes carboxylation of $C{O}_2$ ribulose 1,5-bisphosphate (RuBP), the primary carbon acceptor. Thus, the correct answer Option B.