The compounds that are subjected to biological oxidation are called ______ in which ____ is the most common.

Options

A. Respiratory substrate, carbohydrate
B. Respiratory substance, protein
C. Respiratory organic substances, fats
D. Respiratory substrate, protein

Answer

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks for the term used to describe compounds that undergo biological oxidation (cellular respiration) and identifies the most common of these compounds.

2. **Identifying the Term**: The compounds that are subjected to biological oxidation are known as **respiratory substrates**. These substrates are essential for cellular respiration as they provide the necessary energy through oxidation.

3. **Identifying the Most Common Respiratory Substrate**: Among the various types of respiratory substrates, **carbohydrates** are the most commonly used by cells. This is because carbohydrates are less reduced compounds, meaning they have fewer carbon-hydrogen (C-H) bonds, making them easier to oxidize compared to fats and proteins.

4. **Hierarchy of Respiratory Substrates**: The preference order for respiratory substrates in cells is as follows:
- Carbohydrates (most preferred)
- Fats (second preference)
- Proteins (least preferred, used only when carbohydrates and fats are unavailable)

5. **Final Answer**: Therefore, the complete answer to the question is: The compounds that are subjected to biological oxidation are called **respiratory substrates**, in which **carbohydrates** is the most common.

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