Question

why photorespiration is considered as a wasteful Process

Answer 1

Thus photorespiration is the wasteful process because,it prevent plant from using their ATP and NADPH to synthesizcarbohydrates.rubisco the enzymes which fixer CO2 during for O2 fixation during photorespiration.
I hope this helps you.

Answer 2

 In C3 plants, at higher conc. of O2, RuBisCO express its oxygenase activity and hence CO2 fixation is decreased.

 Here the RuBP, instead of being converted to 2 molecules of PGA, binds with O2 to form 1 molecule of phosphoglycerate

(PGA-3C) and phosphoglycolate (PG-2C).

This pathway is called photorespiration. (It is named so as it utilise O2 and release CO2).

 In the photorespiratory pathway, 25-50 % CO2 that is fixed is released with the utilisation of ATP. There is neither synthesis

of sugars, nor of ATP. Therefore, photorespiration is a wasteful process.