How do plants and cyanobacteria produce net positive oxygen if they need to also metabolize oxygen for energy production?

Question

As I understand, plants use 6 carbon dioxide molecules to make 6 Oxygen molecules and 1 glucose molecule. However, to metabolize that glucose to use as an energy source requires using up another 6 Oxygen molecules, with no net production of oxygen. How did the Great Oxidation Event happen if oxygen produced by photosynthesis needs to also be burned when metabolizing the glucose?

In: 2

Answer 1

The structures that they create are net oxygen positive, if you then burn the entire structure like trees or historically speaking oil and coal then you are releasing the carbon dioxide that the plant locked up and use up the oxygen.