question_answer

First stable product of \[{{C}_{3}}\] pathway is:

A)  Oxalo-acetic acid

B)  3 phosphoglyceric acid

C)  RuBP

D)  Phosphoenol pyruvate

Correct Answer: B

Solution :

In \[{{C}_{3}}\] cycle of photosynthesis RuBP (Ribulose 1- 5-biphosphate) accept \[C{{O}_{2}}\] 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). \[RuBP+C{{O}_{2}}\xrightarrow[{}]{RuBp\,\,carboxylase}2\,carboxy,\,3-keto\] 1, 5-biphosphoribotol       In \[{{C}_{4}}\] pants (\[{{C}_{4}}\]-cycle) the \[C{{O}_{2}}\] is accepted  by phosphoenol pyruvate in mesophyll cells  chloroplast. Oxaloacetic acid (oxaloacetate is formed by the reaction (first product). \[PEP\text{ }+\text{ }C{{O}_{2}}+\text{ }{{H}_{2}}O\xrightarrow[Carboxylase]{PEP}\] Oxaloacetic acid \[+{{H}_{3}}P{{O}_{4}}\]