Final answer:
Higher oxygen levels inhibit the rate of photosynthesis due to competitive inhibition of Rubisco, while increasing oxygen concentration can boost photosynthesis under certain conditions.
Step-by-step explanation:
The effect of oxygen concentration on the rate of photosynthesis depends on the specific conditions. Under normal conditions, higher oxygen levels inhibit the rate of photosynthesis due to competitive inhibition of ribulose bisphosphate carboxylase (Rubisco), the enzyme responsible for carbon dioxide fixation. This is because oxygen competes with carbon dioxide for the active site of Rubisco. On the other hand, under certain conditions such as low carbon dioxide concentration, increasing oxygen concentration can boost the rate of photosynthesis. This is because at low carbon dioxide levels, the inhibition of photosynthesis by oxygen is less pronounced.