Which of the following is an important intermediate formed in all types of respiration ?

Options

A. Acetyl CoA
B. Oxaloacetate
C. Pyruvic acid
D. Tricarboxylic acid.

Answer

To solve the question "Which of the following is an important intermediate formed in all types of respiration?", we will analyze the options provided and understand the role of each in the respiration process.

### Step-by-Step Solution:

1. **Understanding Types of Respiration**:
- There are two main types of respiration: **aerobic respiration** (which requires oxygen) and **anaerobic respiration** (which occurs in the absence of oxygen).

2. **Identifying the Key Intermediates**:
- The question asks for an intermediate that is formed in both types of respiration. We need to evaluate each option:
- **Acetyl CoA**: This is formed during aerobic respiration when pyruvic acid is converted in the presence of oxygen. It is not formed during anaerobic respiration.
- **Oxaloacetate**: This is a part of the TCA (Krebs) cycle, which is specific to aerobic respiration. It is not formed in anaerobic respiration.
- **Pyruvic Acid**: This is produced from glucose during glycolysis, which is the first step in both aerobic and anaerobic respiration. It serves as a key intermediate that can further proceed to either aerobic or anaerobic pathways.
- **Tricarboxylic Acid**: This refers to the TCA cycle, which again is specific to aerobic respiration and does not occur in anaerobic respiration.

3. **Conclusion**:
- Among the options, **pyruvic acid** is the only intermediate that is formed in both aerobic and anaerobic respiration. Therefore, the correct answer is **pyruvic acid**.

### Final Answer:
**C. Pyruvic Acid**