Question

Photorespiration occurs in
(a)Ribosomes
(b)Mitochondria
(c)Peroxisomes
(d)Both B and C

Answer 1

Photorespiration may be a respiratory process in many higher plants. It is often referred to as the oxidative photosynthetic carbon cycle or ${ C }_{ 2 }$ photosynthesis.

Complete answer:
Photorespiration occurs in Ribosome and Mitochondria. It is a chemical process in which the oxygenation of RuBP by RUBISCO is followed by photorespiratory glycolate metabolism. It involves a posh network of enzyme reactions that exchange metabolites between chloroplasts, leaf peroxisomes, and mitochondria.
Photorespiration is a wasteful pathway that competes with the Calvin cycle.It does not generate ATP. It does use oxygen and it does generate carbon dioxide, and it uses a sugar-phosphate as its key fuel.

Additional Information: -In ${ C }_{ 3 }$plants, RuBisCO binds to oxygen molecules and therefore the reaction deviates from the regular metabolic pathway. The mixture of RuBP and oxygen molecules results in the formation of 1 molecule of phosphoglycerate and phosphoglycolate. This pathway is named photorespiration. During photorespiration, no sugar or ATP molecules are synthesized, but just ${ CO }_{ 2 }$ is released at the expense of ATP. And therefore the whole process is futile.
-However, ${ C }_{ 4 }$ plants don't undergo photorespiration due to their special mechanism to extend the ${ CO }_{ 2 }$ level for enzyme binding. During the Hatch and Slack Pathway, the ${ C }_{ 4 }$acid, oxaloacetic acid (OAA) breaks right down to release ${ CO }_{ 2 }$. This ensures the high concentration of intercellular ${ CO }_{ 2 }$. Thus, in ${ C }_{ 4 }$ plants, RuBisCO is more active as a carboxylase enzyme instead of as oxygenase. This is often why C4 plants have better productivity.
So the correct answer is ‘Both B and C’.

Note: The difference between photosynthesis and photorespiration is that Photosynthesis occurs when the RuBisCO enzyme reacts with carbon dioxide. However, the photorespiration occurs when the RuBisCO enzyme reacts with oxygen.