`C_(4)` plants differ from `C_(3)` plants with respect to

Options

A. First product
B. Substrate which accepts carbon dioxide
C. Number of ATP molecules consmed
D. All the above

Answer

To solve the question regarding how C4 plants differ from C3 plants, we will analyze the key differences in their photosynthetic processes step by step.

### Step-by-Step Solution:

1. **Identify the First Product of Photosynthesis**:
- In C3 plants, the first product of the Calvin cycle is a three-carbon compound known as phosphoglyceric acid (PGA).
- In C4 plants, the first product is a four-carbon compound called oxaloacetic acid (OAA).

**Hint**: Remember that C3 plants produce a 3-carbon compound while C4 plants produce a 4-carbon compound.

2. **Identify the Carbon Dioxide Acceptor**:
- C3 plants utilize ribulose 1,5-bisphosphate (RUBP) as the carbon dioxide acceptor.
- C4 plants use phosphoenolpyruvate (PEP) as the carbon dioxide acceptor.

**Hint**: C3 plants use RUBP, while C4 plants use PEP for carbon fixation.

3. **Determine the Number of ATP Molecules Consumed**:
- C3 plants consume a total of 18 ATP molecules during the photosynthetic process.
- C4 plants consume about 30 ATP molecules to complete the same process.

**Hint**: C4 plants require more ATP compared to C3 plants due to their additional steps in the photosynthetic pathway.

4. **Summarize the Differences**:
- C4 plants differ from C3 plants in:
- The first product of photosynthesis (3-carbon vs. 4-carbon).
- The substrate that accepts carbon dioxide (RUBP vs. PEP).
- The number of ATP molecules consumed (18 vs. 30).

5. **Conclusion**:
- Since all the mentioned aspects differ between C4 and C3 plants, the correct answer to the question is "all of the above."

**Final Answer**: All of the above.