The number of ATP required in mosophyll cells of `C_3` plants and bundle sheath cells of `C_4` plants respectively for net export of 12 G - 3 -P during dark reaction

Options

A. 108 and 180
B. 18 and 30
C. 18 and 18
D. 108 and 108

Answer

To solve the question regarding the number of ATP required in mesophyll cells of C3 plants and bundle sheath cells of C4 plants for the net export of 12 G-3-P during the dark reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Dark Reaction**:
- The dark reaction, also known as the Calvin cycle, is a series of biochemical reactions in photosynthesis that do not require light. It uses ATP and NADPH produced in the light reactions to convert carbon dioxide into glucose.

2. **C3 Plants**:
- In C3 plants, the dark reaction occurs in the mesophyll cells. For every molecule of G-3-P produced, 3 ATP are consumed.
- To export 12 G-3-P, we calculate the total ATP required:
\[ \text{ATP required} = 12 \, \text{G-3-P} \times 3 \, \text{ATP/G-3-P} = 36 \, \text{ATP} \]

3. **C4 Plants**:
- In C4 plants, the dark reaction occurs in the bundle sheath cells. The process is more complex as it involves the fixation of carbon dioxide into a four-carbon compound (oxaloacetate) in mesophyll cells, which is then transported to bundle sheath cells.
- For the net export of 12 G-3-P, the ATP requirement is higher. In C4 plants, it takes 6 ATP to produce 1 G-3-P. Therefore, to find the total ATP required:
\[ \text{ATP required} = 12 \, \text{G-3-P} \times 6 \, \text{ATP/G-3-P} = 72 \, \text{ATP} \]

4. **Final Calculation**:
- The total ATP required for the net export of 12 G-3-P from C3 and C4 plants would be:
- C3 plants (mesophyll cells): 36 ATP
- C4 plants (bundle sheath cells): 72 ATP

5. **Conclusion**:
- The number of ATP required in mesophyll cells of C3 plants and bundle sheath cells of C4 plants respectively for the net export of 12 G-3-P during the dark reaction is:
- C3 plants: 36 ATP
- C4 plants: 72 ATP

### Final Answer:
- The answer is 36 ATP for C3 plants and 72 ATP for C4 plants.