MDCAT Biology MCQ #556

The enzyme Rubisco can catalyze two different reactions. What determines whether it functions as a carboxylase or an oxygenase?

MDCAT Biology MCQ #556

  1. Question 1

    Q1. The enzyme Rubisco can catalyze two different reactions. What determines whether it functions as a carboxylase or an oxygenase?

    • A) The temperature of the surrounding environment
    • B) The relative concentrations of CO2 and O2
    • C) The availability of ATP and NADPH in the stroma
    • D) The intensity of light hitting the thylakoids

    Answer: The relative concentrations of CO2 and O2

    Explanation: Rubisco acts as a carboxylase when CO2 is high but as an oxygenase when O2 is high, leading to photorespiration.