Question

During photorespiration, the oxygen consuming reaction(s) occur in -

• A. Stroma of chloroplasts
• B. Stroma of chloroplasts and mitochondria
• C. Stroma of chloroplasts and peroxisomes
• D. Grana of chloroplasts and peroxisomes

Answer 1

Answer: (C)

Stroma of chloroplasts and peroxisomes

Answer 2

Photorespiration is a process the rate of which increases under the influence of light, CO2, is released and O2 is used but no ATP is formed. It involves three organelles chloroplasts, mitochondria and peroxisomes. In chloroplast O2 is utilized as, ribulose biphosphate is oxidized and a molecule of phosphoglycolic acid and a molecules of 3-phosphoglyceric acid are formed. This oxidation takes place under the influence of high light intensity. Ribulose diphosphate carboxylase, an enzyme, facilitates this reaction as it behaves as an oxygenase. Only one molecule of oxygen is fixed here.