Respiratory enzymes are mostly located in

Options

A. mitochondrial matrix
B. Perimitochondrial space
C. Cristae
D. Outer membrane

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks where respiratory enzymes are mostly located in plants.

2. **Identifying Key Terms**: The term "respiratory enzymes" refers to the enzymes involved in the process of respiration, which is crucial for energy production in cells.

3. **Location of Respiratory Enzymes**:
- The primary site for respiration in eukaryotic cells, including plant cells, is the mitochondria.
- Within the mitochondria, there are specific areas: the outer membrane, the inner membrane, the intermembrane space, and the mitochondrial matrix.

4. **Function of the Mitochondrial Matrix**:
- The mitochondrial matrix is where the Krebs cycle (also known as the citric acid cycle) occurs. This cycle is essential for the breakdown of glucose and the production of ATP (adenosine triphosphate), the energy currency of the cell.
- The matrix contains a high concentration of respiratory enzymes that facilitate these biochemical reactions.

5. **Conclusion**: Based on the information, it is clear that the respiratory enzymes are mostly located in the mitochondrial matrix.

6. **Final Answer**: The correct answer is the **mitochondrial matrix**.