During photorespiration, the oxygen consuming reaction(s) occur in
- stroma of chloroplasts
- stroma of chloroplasts and mitochondria
- stroma of chloroplasts and peroxisomes
- grana of chloroplasts and peroxisomes
Answer
(3) stroma of chloroplasts and peroxisomes
Solution
As per NCERT, in photorespiration RuBisCO binds O2 instead of CO2 and RuBP gives one molecule of phosphoglycerate and one of phosphoglycolate; the pathway involves chloroplast, peroxisome and mitochondria.
∵ O2 is consumed (i) in the stroma of chloroplasts — oxygenation of RuBP by RuBisCO, and (ii) in peroxisomes — oxidation of glycolate to glyoxylate by glycolate oxidase.
∵ In mitochondria CO2 is released, not O2 consumed; grana carry out the light reaction ⇒ (2) and (4) are wrong.
Answer: (3)