2003 AIPMT Photosynthesis in Higher PlantsPhotorespiration Medium Question 7 of 7 in Photorespiration

Which one of the following is wrong in relation to photorespiration : -

A It occurs in chloroplasts
B It occurs in daytime only
C It is a characteristic of $C_4$ plants
D It is a characteristic of $C_3$ plants

The answer is C.

Solution

Photorespiration occurs when RuBisCO uses $O_2$ instead of $CO_2$ (oxygenase activity), producing phosphoglycolate. It involves three organelles: chloroplasts, peroxisomes and mitochondria, and it starts in the chloroplast; true.
It depends on light (it occurs only in the daytime, along with photosynthesis); true.
It is a characteristic feature of $C_3$ plants, especially at high temperature and high $O_2$; true.
In $C_4$ plants, the $C_4$ pathway concentrates $CO_2$ around RuBisCO in the bundle sheath cells, so its oxygenase activity is suppressed and photorespiration is negligible. So it is not a characteristic of $C_4$ plants.
So the wrong statement is that photorespiration is a characteristic of $C_4$ plants.

Concept Photorespiration absent in C4 plants

Photorespiration in past papers

7 questions from this chapter have appeared across 6 exam years.