Photorespiration
A) may be an evolutionary relic from when atmospheric O2 levels were low.
B) is of benefit to the plant since it breaks down rubisco.
C) is attributable to high CO2 levels.
D) produces glucose.

Question

Quizplus · Accepted Answer

Photorespiration is thought to be an evolutionary relic from when atmospheric O2 levels were low. This is because it can occur when rubisco (the enzyme responsible for carbon fixation in photosynthesis) binds with O2 instead of CO2, leading to the production of a toxic compound that must be broken down in a process known as photorespiration. With lower atmospheric O2 levels, the likelihood of O2 binding to rubisco was lower, so photorespiration was not as necessary. As atmospheric O2 levels increased, photorespiration became more common as a way for plants to deal with this problem. However, photorespiration is not beneficial to the plant because it uses energy and does not produce glucose.