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Multiple Choice
Why is it necessary for six molecules of CO$_2$ to enter the chloroplast during photosynthesis?
A
To produce one molecule of glucose (C$_6$H$_{12}$O$_6$)
B
To initiate the light-dependent reactions
C
To generate six molecules of ATP
D
To release six molecules of oxygen (O$_2$)
Verified step by step guidance
1
Understand the process of photosynthesis: Photosynthesis occurs in two main stages - the light-dependent reactions and the Calvin cycle (light-independent reactions). The Calvin cycle is where carbon dioxide (CO$_2$) is used to synthesize glucose (C$_6$H$_{12}$O$_6$).
Recall the molecular formula of glucose: Glucose has the chemical formula C$_6$H$_{12}$O$_6$, which means it contains six carbon atoms. These carbon atoms must come from the CO$_2$ molecules that enter the chloroplast.
Determine the role of CO$_2$ in the Calvin cycle: During the Calvin cycle, each molecule of CO$_2$ contributes one carbon atom. To form one molecule of glucose, six carbon atoms are required, which means six molecules of CO$_2$ are necessary.
Eliminate incorrect options: The light-dependent reactions do not directly require CO$_2$, as they focus on capturing light energy to produce ATP and NADPH. Similarly, CO$_2$ is not directly involved in generating ATP or releasing oxygen (O$_2$), as these processes occur during the light-dependent reactions.
Conclude the correct answer: The six molecules of CO$_2$ are required to provide the carbon atoms needed to synthesize one molecule of glucose (C$_6$H$_{12}$O$_6$) during the Calvin cycle.