Question

In the given figure, what are the substances labelled as $P,Q,R$ and $S$?

• A. P-PGA, Q-Glyoxylate, $R-N{H}_3$, S-Serine
• B. P-Glycolate, Q-Glyoxylate, $R-N{H}_3$, S-Serine
• C. P-Glycolate, Q-Glyoxylate, $R-C{O}_2$, S-Serine
• D. P-RuBP, Q-Glycerate, $R-C{O}_2$, S-Serine

Answer 1

Answer: (B)

The given diagram represents $C_2$ cycle or photorespiration. The process has following steps:

•Oxygen binds with RuBP oxygenase and forms phosphoglycolate in chloroplast which gets converted to glycolate and is transported to peroxisomes.

•In peroxisomes it forms glyoxylate and then glycine.

•Glycine then enters the mitochondria and looses $N{H}_4$ and $C{O}_2$ and forms serine.

•Serine is transported to peroxisomes and in a series of reactions it forms glycerate which gets converted to PGA or Phosphoglyceric Acid and then RuBP in the chloroplast.

So, the correct answer is B.