Chloroplast, peroxisome and mitochondria are three cellular organelles involved in photorespiration.
Various steps of photorespiratory pathway:
(a) In presence of high Oz, RuBP carboxylase acts as oxygenase and results in formation of 3PGA (Phosphoglyeric acid) and 2-phosphoglycolate, 2-phosphoglycolate loses PO4 group to make glycolate.
(b) Synthesized glycolate in chloroplast enters into peroxisomes.
© The glycolate is oxidised into glyoxylate and H2O2 by oxidase enzyme.
(d) Glyoxylate is changed into glycine (amino acid) by glutamate glyoxylate transaminase (enzyme).
(e) Two molecules of glycine form serine and one mol. of CO2 in mitochondria but no ATP and NADPH are formed.
(f) Finally serine passes into mitochondria and is changed into carbohydrate (3 carbon) and Phosphoglycolate (2 carbon).
(g) Soon glycolate is formed of phosphoglycolate. In peroxisomes, glycolate soon changes into glycine and glycine into serine and CO2, without production of assimilatory powers (ATP and NADPH2).