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Multiple Choice
Why is it necessary for 6 molecules of CO$_2$ to enter the chloroplast during photosynthesis?
A
To generate six molecules of ATP
B
To produce one molecule of glucose (C$_6$H$_{12}$O$_6$)
C
To release six molecules of oxygen (O$_2$)
D
To initiate the light-dependent reactions
Verified step by step guidance
1
Understand the role of CO$_2$ in photosynthesis: CO$_2$ is a key reactant in the Calvin cycle, which is part of the light-independent reactions of photosynthesis. It is used to build glucose molecules through a series of enzymatic reactions.
Recall the chemical formula for glucose: Glucose has the molecular formula C$_6$H$_{12}$O$_6$, meaning it contains six carbon atoms. These carbon atoms come from six molecules of CO$_2$ that are fixed during the Calvin cycle.
Recognize the stoichiometry of the Calvin cycle: Each turn of the Calvin cycle fixes one molecule of CO$_2$. To produce one molecule of glucose, the cycle must turn six times, requiring six molecules of CO$_2$.
Understand the relationship between CO$_2$ and oxygen release: While six molecules of CO$_2$ are used in the Calvin cycle, oxygen (O$_2$) is released during the light-dependent reactions as a byproduct of water splitting, not directly related to CO$_2$ fixation.
Clarify the role of ATP: ATP is generated during the light-dependent reactions and used as an energy source in the Calvin cycle to drive the synthesis of glucose. However, the entry of six molecules of CO$_2$ is specifically tied to the production of one molecule of glucose, not directly to ATP generation.