Question

Warburg effect refers to

• A. Decreased photosynthetic rate at very high oxygen concentration
• B. Increased photosynthetic rate at very high oxygen concentration
• C. Decreased photosynthetic rate at very low oxygen concentration
• D. Increased photosynthetic rate at very low carbon dioxide concentration

Answer 1

The correct option is A Decreased photosynthetic rate at very high oxygen concentration

Oxygen is a byproduct of photosynthesis generated during the photolysis of water. Oxygen also has a limiting effect on photosynthesis.
As oxygen concentration increases in the cells, it competes with carbon dioxide for binding with the enzyme RuBP carboxylase. Binding of oxygen to RuBisCo changes the function of RuBP-carboxylase to that of RuBP-oxygenase and adds an oxygen to the RuBP. This increases photorespiration, reduces the fixation of carbon dioxide to glucose and reduces the efficiency and output of photosynthesis. This phenomenon is referred to as Warburg effect.