MDCAT Biology MCQ #169

A researcher uses heavy isotope oxygen-18 to trace the source of atmospheric oxygen released by algae. Which molecule is the oxygen derived from?

MDCAT Biology MCQ #169

  1. Question 1

    Q1. A researcher uses heavy isotope oxygen-18 to trace the source of atmospheric oxygen released by algae. Which molecule is the oxygen derived from?

    • A) Carbon dioxide
    • B) Water
    • C) Glucose
    • D) Chlorophyll a

    Answer: Water

    Explanation: Photolysis of water provides electrons to PSII and releases oxygen; CO2 is used in the dark reactions, not for oxygen production.