Examkin

Question

Difficulty: EasyPlant Nutrition and Photosynthesis

During the light-dependent stage of photosynthesis, oxygen gas is released into the atmosphere as a byproduct. Which of the following processes is directly responsible for the release of this oxygen?

  1. A
    The reduction of carbon dioxide during the Calvin cycle
  2. The photolysis of water moleculesAnswer
  3. C
    The translocation of organic nutrients through phloem vessels
  4. D
    The oxidative breakdown of glucose during cellular respiration

Answer

The photolysis of water molecules is directly responsible for releasing oxygen gas during photosynthesis.
Photolysis of water molecules occurs when light energy absorbed by chlorophyll splits water into hydrogen ions, electrons, and oxygen gas (O2O_2). This reaction takes place inside the thylakoid membranes during the light-dependent stage of photosynthesis.

Step-by-Step Solution

1
Identify the biological origin of oxygen evolved during photosynthesis.
Oxygen gas originates exclusively from the splitting of water molecules during the light-dependent phase.
Absorbed light energy drives the photolysis of water (2H2O→4H++4e−+O22H_2O \rightarrow 4H^+ + 4e^- + O_2) inside the thylakoid lumen.
2
Distinguish light-dependent reactions from light-independent carbon fixation.
Photolysis generates oxygen gas in the thylakoids, whereas carbon dioxide assimilation forms sugar in the stroma.
Carbon dioxide contributes to the synthesis of glucose, not the free molecular oxygen released into the atmosphere.

Key Concept

Photolysis of Water in Photosynthesis
Rate this question

Topics

Plant Nutrition and Photosynthesis

More questions from this topic