Solution:
Photorespiration is a type of respiration which occurs in green cells in presence of light. It involves three organelles - chloroplast, peroxisomes and mitochondria. Respiratory substrate in photorespiration is a 2-carbon compound glycolic acid (2C), hence called \(\mathrm{C}\), cycle. RuBP-carboxylase in normal \(\mathrm{O}_{2} / \mathrm{CO}_{2}\) conc, acts as 'carboxylase'. It is the key enzyme of photosynthesis in \(\mathrm{C}_{3}\) plants.