Which bonds are broken down by oxidation in a respiratory substrate?

Options

A. `C=O`
B. `C-H`
C. `C-C`
D. `C-N`

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which specific bonds are broken down during the oxidation of a respiratory substrate in the process of respiration.

2. **Identifying the Respiratory Substrate**: In most organisms, including humans, the primary respiratory substrate is glucose (C6H12O6). This compound is broken down during cellular respiration to release energy.

3. **Process of Cellular Respiration**: Cellular respiration involves several biochemical pathways where glucose is oxidized to produce ATP (adenosine triphosphate), which is the energy currency of the cell.

4. **Bonds Involved in Glucose**: Glucose contains several types of chemical bonds, including:
- Carbon-Carbon (C-C) bonds
- Carbon-Hydrogen (C-H) bonds
- Carbon-Oxygen (C-O) bonds

5. **Oxidation and Energy Release**: During the oxidation of glucose, the breaking of bonds releases energy. The most significant bonds that are broken during this process are the Carbon-Carbon (C-C) bonds.

6. **Conclusion**: Therefore, the bonds that are primarily broken down by oxidation in a respiratory substrate like glucose are the **Carbon-Carbon (C-C) bonds**.

### Final Answer:
The bonds that are broken down by oxidation in a respiratory substrate are the **Carbon-Carbon (C-C) bonds**.

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