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Multiple Choice
What is the basic role of \( \mathrm{CO}_2 \) in photosynthesis?
A
It serves as a carbon source for the synthesis of glucose.
B
It absorbs sunlight to initiate the process.
C
It provides electrons for the electron transport chain.
D
It acts as an energy carrier during the light reactions.
Verified step by step guidance
1
Understand the process of photosynthesis: Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. It occurs in two main stages: the light-dependent reactions and the Calvin cycle (light-independent reactions).
Identify the role of carbon dioxide (
): Carbon dioxide is used during the Calvin cycle, where it is fixed into organic molecules to form glucose. This process is known as carbon fixation.
Clarify the incorrect options:
- Carbon dioxide does not absorb sunlight; chlorophyll in the chloroplasts absorbs sunlight to initiate the light-dependent reactions.
- Carbon dioxide does not provide electrons for the electron transport chain; water (
) is the source of electrons.
- Carbon dioxide does not act as an energy carrier; molecules like ATP and NADPH serve as energy carriers during photosynthesis.
Explain the correct answer: Carbon dioxide serves as the carbon source for the synthesis of glucose during the Calvin cycle. It is combined with ribulose-1,5-bisphosphate (RuBP) by the enzyme RuBisCO to form 3-phosphoglycerate (3-PGA), which is later converted into glucose.
Summarize the importance of carbon dioxide: Without carbon dioxide, plants would not be able to synthesize glucose, which is essential for their energy needs and growth. This highlights the critical role of carbon dioxide in the process of photosynthesis.