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Difficulty: EasyPlant Nutrition and Photosynthesis

During the light-dependent stage of photosynthesis, oxygen gas is released as a byproduct. Which of the following chemical compounds is the direct source of this liberated oxygen?

  1. Water molecules split during photolysisAnswer
  2. B
    Carbon dioxide molecules reduced during the Calvin cycle
  3. C
    Organic sugars translocated through phloem tissue
  4. D
    Mineral salts absorbed by root hair cells from soil water

Answer

Water molecules split during photolysis
During the light-dependent stage of photosynthesis, light energy absorbed by chlorophyll triggers the photolysis (light splitting) of water (H2OH_2O) inside the thylakoids. This reaction breaks water into hydrogen ions, electrons (which replenish photosystem II), and oxygen gas (O2O_2), which diffuses out of the plant through stomata.

Step-by-Step Solution

1
Identify the photochemical reaction responsible for oxygen liberation during photosynthesis.
Absorbed light energy drives the photolysis of water (H2OH_2O) molecules in the chloroplast thylakoids, releasing hydrogen ions, electrons, and molecular oxygen (O2O_2).
Photolysis of water is the fundamental light-dependent reaction step that produces gaseous oxygen.

Key Concept

Photolysis of water as the source of oxygen in photosynthesis
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Topics

Plant Nutrition and Photosynthesis

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