Which of the statements is not true of the `C_(4)` pathway

Options

A. Overcomes loss due to photorespiration
B. The `CO_(2)` acceptor is a `C_(3)` compound
C. Inhibited by low `CO_(2)` concentration
D. Required more energy than the `C_(3)` pathways fir production of glucose

Answer

To determine which statement is not true regarding the C4 pathway, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the C4 Pathway**:
- The C4 pathway is a photosynthetic process found in certain plants (C4 plants) that have adapted to high temperatures and low CO2 concentrations. This pathway involves the fixation of CO2 into a four-carbon compound.

2. **Evaluating Each Statement**:
- **Statement 1**: "Overcome loss due to photorespiration."
- This statement is **true**. C4 plants have adaptations that minimize photorespiration, allowing them to efficiently use CO2 even when concentrations are low.

- **Statement 2**: "The CO2 acceptor is a C3 compound."
- This statement is **not true**. In C4 plants, the CO2 acceptor is not a C3 compound; instead, it is a four-carbon compound (oxaloacetate) formed from the reaction of CO2 with phosphoenolpyruvate (PEP), which is a three-carbon compound. However, the initial fixation occurs in the mesophyll cells, leading to the formation of a four-carbon compound.

- **Statement 3**: "Inhibited by low CO2 concentration."
- This statement is **true**. C4 plants are designed to be more efficient under low CO2 conditions, but their photosynthetic activity can still be inhibited if CO2 levels drop too low.

- **Statement 4**: "Required more energy than the C3 pathways for production of glucose."
- This statement is **true**. C4 plants require more ATP for the synthesis of glucose compared to C3 plants. It is estimated that C4 plants use about 30 ATP molecules to produce one glucose molecule, while C3 plants use about 18 ATP molecules.

3. **Conclusion**:
- The statement that is **not true** regarding the C4 pathway is **Statement 2**: "The CO2 acceptor is a C3 compound."

### Final Answer:
The statement that is not true of the C4 pathway is: **"The CO2 acceptor is a C3 compound."**