Series of events during photorespiration:

Chloroplast: RuBP instead of being converted to 2 molecules of PGA binds with O2 to form one molecule of phosphoglycerate and phosphoglycolate (2 Carbon). Phosphoglycolate is further converted into glycolate through a series of reactions.

Peroxisome: Glycolate is trasnsported to the Peroxisomes where it gets converted into glyoxylate and then into Glycine and Hydrogen peroxide (H2O2) is generated as a byproduct.

Mitochondria: Glycine is further transported to Mitochondria where it under a series of reactions to produce another amino acid serine. During this conversion ammonia and carbon dioxide are released and energy is generated through respiration. ATP and NADPH are used in consumed thereby reducing the overall efficiency of energy production. Serine is further converted back into Glyceric acid that can be used in calvin cycle for carbon fixation. Briefly, serine enters peroxisome where it gets converted int hydropyruvic acid and then to glyceric acid. Glyceric acid is transported to Chloroplasts where it is converted to 3phosphoglyceric acid and can be used in calvin cycle for carbon fixation.