Multiple Choice
In the context of photosynthesis, where does the energy found in food molecules originally come from?
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9. Photosynthesis
Introduction to Photosynthesis
Multiple Choice
In the process of photosynthesis, what is the primary source of the oxygen gas (O_2) released by plants?
A
Carbon dioxide (CO_2)
B
Chlorophyll
C
Water (H_2O)
D
Glucose (C_6H_{12}O_6)
Verified step by step guidance1
Understand the process of photosynthesis: Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen as byproducts. It occurs in two main stages: the light-dependent reactions and the Calvin cycle.
Focus on the light-dependent reactions: During these reactions, light energy is absorbed by chlorophyll and other pigments in the thylakoid membranes of chloroplasts. This energy is used to split water molecules (H₂O) in a process called photolysis.
Break down photolysis: Photolysis involves the splitting of water molecules into oxygen gas (O₂), protons (H⁺), and electrons. The oxygen gas is released as a byproduct into the atmosphere, while the protons and electrons are used in subsequent steps of photosynthesis.
Clarify the role of water (H₂O): Water is the primary source of the oxygen gas (O₂) released during photosynthesis. The oxygen atoms in water molecules are liberated during photolysis and combine to form O₂ gas.
Connect the answer to the question: Based on the process of photolysis in the light-dependent reactions, the correct answer is water (H₂O), as it is the source of the oxygen gas released by plants during photosynthesis.
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