Why is it necessary for six molecules of CO\(_2\) to enter the chloroplast during photosynthesis?

• A. Because six CO\(_2\) molecules are required to synthesize one molecule of glucose (C\(_6\)H\(_{12}\)O\(_6\)).
• B. Because six CO\(_2\) molecules are required to initiate the light-dependent reactions.
• C. Because each CO\(_2\) molecule produces one ATP molecule during the Calvin cycle.
• D. Because six CO\(_2\) molecules are needed to generate six molecules of oxygen gas.

Answer: (A)

Verified step by step guidance

1. Step 1: Begin by understanding the process of photosynthesis, which consists of two main stages: the light-dependent reactions and the Calvin cycle (light-independent reactions). The Calvin cycle is responsible for synthesizing glucose (C\(_6\)H\(_{12}\)O\(_6\)) using carbon dioxide (CO\(_2\)).
2. Step 2: Recall the chemical formula for glucose: C\(_6\)H\(_{12}\)O\(_6\). This molecule contains six carbon atoms, which must come from six molecules of CO\(_2\). Each CO\(_2\) molecule contributes one carbon atom to the glucose molecule.
3. Step 3: Understand that the Calvin cycle operates in a series of steps where CO\(_2\) is fixed into organic molecules. Specifically, six CO\(_2\) molecules are required to complete the cycle and produce one molecule of glucose.
4. Step 4: Clarify that the light-dependent reactions do not directly use CO\(_2\). Instead, they generate ATP and NADPH, which are energy carriers used in the Calvin cycle to drive the synthesis of glucose from CO\(_2\).
5. Step 5: Note that oxygen gas (O\(_2\)) is produced during the light-dependent reactions as a byproduct of splitting water (H\(_2\)O), not from CO\(_2\). Therefore, the six CO\(_2\) molecules are not involved in generating oxygen gas.