Q. First stable product of $ C_{3} $ pathway is:
Delhi UMET/DPMTDelhi UMET/DPMT 2006
Solution:
In $C _{3}$ cycle of photosynthesis RuBP (Ribulose $1- 5$-biphosphate) accept $CO _{2}$ and converted into a transient intermediate compound called $2$-carboxy $3$keto $1-5$-biphospho ribotol which immediately splits into $2$ molecules of $3$ phosphoglyceric acid (first stable product).
$R u B P+C O_{2} \ce{->[RuBp \,\text{carboxylase}]} 2$ carboxy, $3-$ keto $1,5$ -biphosphoribotol In $C _{4}$ pants ( $C _{4}$-cycle) the $CO _{2}$ is accepted by phosphoenol pyruvate in mesophyll cells chloroplast. Oxaloacetic acid (oxaloacetate is formed by the reaction (first product).
$P E P+ CO _{2}+ H _{2} O \ce{->[PEP][\text{Carboxylase}]}$ Oxaloacetic acid $+ H _{3} PO _{4}$
