What problem can arise when Rubisco uses O2 instead of CO2?

Rubisco, the enzyme responsible for capturing carbon dioxide during photosynthesis, can also bind to oxygen, especially at high temperatures or when CO2 concentrations are low. When Rubisco uses O2 instead of CO2, it leads to a process known as photorespiration.

Photorespiration is a wasteful pathway that occurs, reducing the efficiency of photosynthesis because it results in the fixation of oxygen rather than carbon. This process decreases the overall yield of glucose since the carbon atoms that could have been used for sugar synthesis are lost in the form of carbon dioxide. In addition to this, the energy and reducing power (in the form of ATP and NADPH) that would be produced during the correct photosynthetic carbon-fixing pathway are wasted during photorespiration.

Thus, when Rubisco uses O2, it diverts resources from the production of carbohydrates, essentially hindering the plant's ability to synthesize energy-rich compounds needed for growth and development. This significant impact on the plant's metabolic processes highlights why the process initiated by Rubisco's use of O2 is critical to understanding plant physiology and efficiency in carbon fixation.