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Q.
First $CO_{2}$ acceptor in $C_{4}$ plants is
AMUAMU 2006
Solution:
In $C _{4}$ plants bundle sheath cells of leaf show $Kranz$ anatomy. In $C _{4}$ plants, the $CO _{2}$ first accepted in the mesophyll cells by PEP (phosphoenol pyruvate) and form a four carbon compound oxaloacetic acid.
Phosphoenol pyruvate $+ CO _{2} \underset{\text { Carboxylase }}{\xrightarrow{\text { PEP }}}$ Oxaloacetic acid
In $C _{3}$ plants, the carboxylation (addition of $CO _{2}$ ) of RuBP (Ribulose 1,5 biphosphate) is catalyzed by an enzyme rubisco to form a 3-carbon compound phosphoglyceric acid (the first stable product of $C_{3}$ plants).
$RuBP + CO _{2} \xrightarrow{\text { Rubisco }} 3$-phosphoglyceric acid
Pyruvic acid is the end product of glycolysis During glycolysis one molecule of glucose is breakdown into two molecules of pyruvic acid.