How many turns of Calvin cycle must occur if 9ATP and 6NADPH+H+ are utilized giving a net gain of one molecule of PGAL?

Options

A. one
B. two
C. three
D. six

Answer

To determine how many turns of the Calvin cycle are required to produce one molecule of PGAL (Phosphoglyceraldehyde) using 9 ATP and 6 NADPH, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Inputs and Outputs of the Calvin Cycle:**
- The Calvin cycle requires ATP and NADPH as energy sources.
- For each turn of the Calvin cycle, the typical energy requirement is:
- 3 ATP
- 2 NADPH

2. **Calculate the Number of Turns Based on ATP:**
- Given that 9 ATP are utilized, we can calculate the number of turns:
\[ \text{Number of turns from ATP} = \frac{\text{Total ATP}}{\text{ATP per turn}} = \frac{9 \text{ ATP}}{3 \text{ ATP/turn}} = 3 \text{ turns} \]

3. **Calculate the Number of Turns Based on NADPH:**
- Given that 6 NADPH are utilized, we can calculate the number of turns:
\[ \text{Number of turns from NADPH} = \frac{\text{Total NADPH}}{\text{NADPH per turn}} = \frac{6 \text{ NADPH}}{2 \text{ NADPH/turn}} = 3 \text{ turns} \]

4. **Determine the Net Gain of PGAL:**
- Each complete cycle of the Calvin cycle produces one molecule of PGAL for every 3 turns of the cycle.
- Since both calculations (from ATP and NADPH) indicate that 3 turns are needed, this confirms that:
- 3 turns of the Calvin cycle will yield a net gain of 1 molecule of PGAL.

5. **Conclusion:**
- Therefore, the total number of turns of the Calvin cycle required to produce one molecule of PGAL with the given inputs is **3 turns**.

### Final Answer:
**3 turns of the Calvin cycle are required to produce one molecule of PGAL.**

---