Question

Identify the ways in which photorespiration drains energy from the plant.

Answer 1

uses energy

Answer 2

loss of fixed carbon

Answer 3

also produces toxic byproducts that need to be taken care of (hydrogen peroxide, free ammonium). the energy consumption of the biochemical reactions involved is actually pretty vast, as you need both ATP and NADH for the entire cycle including regeneration of the byproducts. imagine that, if your RuBisCO uses one oxygen molecule, that it has to build in at least two CO2 molecules to just make up for the loss.

photorespiration always occurs under natural circumstances (meaning <1% CO2 in the athmosphere) and is a major cause for C3 plants being ineffective.