AP BIOLOGY

Detailed explanation-1: -Although the hydrogen atoms from the water molecules are used in the photosynthesis reactions, the oxygen molecules are released as oxygen gas (O2).

Detailed explanation-2: -Oxygen (O2) is evolved during photosynthetic electron transport when water is split by the oxygen-evolving complex to provide protons and electrons to the chloroplastic electron chain, thereby generating ATP and NADPH-the energy source and reducing power for plant metabolism.

Detailed explanation-3: -Yes, oxygen is produced in the light reaction of photosynthesis in lumen thylakoid by the photolysis of water.

Detailed explanation-4: -Oxygen liberated during photosynthesis comes from the splitting or hydrolysis of water in the green plants. Cornelius van Niel experimentally proved for the first time that the oxygen liberated during photosynthesis comes from water and not from carbon dioxide.