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Multiple Choice
What is the importance of the carbon dioxide (CO$_2$) cycle in photosynthesis?
A
It provides the carbon source for the synthesis of organic molecules in plants.
B
It breaks down glucose to release energy for plant growth.
C
It supplies oxygen directly to plant cells for cellular respiration.
D
It generates ATP as the primary energy currency of the cell.
Verified step by step guidance
1
Understand the role of carbon dioxide (CO$_2$) in photosynthesis: CO$_2$ is a key reactant in the Calvin cycle, which is part of the photosynthetic process. It provides the carbon atoms needed to synthesize glucose and other organic molecules.
Recall the overall equation for photosynthesis: 6CO$_2$ + 6H$_2$O + light energy → C$_6$H$_{12}$O$_6$ + 6O$_2$. This shows that CO$_2$ is directly involved in forming glucose (C$_6$H$_{12}$O$_6$).
Clarify the incorrect options: Breaking down glucose to release energy is part of cellular respiration, not photosynthesis. Supplying oxygen for cellular respiration is also unrelated to the CO$_2$ cycle in photosynthesis. Generating ATP occurs in the light-dependent reactions, not directly through the CO$_2$ cycle.
Focus on the correct answer: The importance of the CO$_2$ cycle in photosynthesis lies in its role as the carbon source for synthesizing organic molecules, which are essential for plant growth and energy storage.
Summarize the concept: The CO$_2$ cycle in photosynthesis is crucial because it enables plants to convert inorganic carbon into organic compounds, forming the basis of energy and biomass production in ecosystems.