Question

In photorespiration, glycolate is converted to $C{O}_2$ and serine in

• A. Chloroplast
• B. Peroxisomes
• C. Vacuoles
• D. Mitochondria

Answer 1

Answer: (D)

Mitochondria

Photorespiration is a process that makes a difference between C3 and C4 plants. It was first observed by Otto Warburg in 1920 that presence of high oxygen concentration and high temperature decrease the rate of photosynthesis.

RuBisCO is the most abundant enzyme and it has the affinity to both $CO_2$ and $O_2$. In C3 plants, when there is high $O_2$ concentration and temperature, $O_2$ binds with RuBisCO instead of $CO_2$ and form one molecule of phosphoglycerate and phosphoglycolate in a pathway known as photorespiration. This process can be understood in the following steps:

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

2. In peroxisomes, it forms glyoxylate and then glycine.

3. Glycine then enters the mitochondria and loses $NH_4$ and $CO_2$ in a reaction and it forms serine.

4. Serine is transported to peroxisomes and in a series of reaction, it forms glycerate which gets converted to Phosphoglyceric Acid (PGA) and then RuBP in the chloroplast.

So, the correct answer is D.