Proteins enter into Krebs' cycle through

Options

A. `prop`-Ketoglutarate
B. OAA
C. both (1) and (2)
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or TCA cycle, is a crucial metabolic pathway that plays a key role in cellular respiration. It involves a series of chemical reactions used by all aerobic organisms to generate energy.

2. **Proteins and Amino Acids**: Proteins are made up of amino acids. During metabolism, proteins can be broken down into their constituent amino acids, which can then enter the Krebs cycle at various points.

3. **Entry Points for Amino Acids**: Amino acids can enter the Krebs cycle at different intermediates. The question specifically asks about proteins entering the cycle, which is primarily through their breakdown into amino acids.

4. **Identifying Intermediates**:
- **Alpha-Ketoglutarate**: Certain amino acids, such as glutamate, can be converted into alpha-ketoglutarate, which is an intermediate in the Krebs cycle.
- **Oxaloacetic Acid (OAA)**: Other amino acids, like aspartate, can be converted into oxaloacetic acid, another key intermediate in the Krebs cycle.

5. **Analyzing the Options**:
- The first option is alpha-ketoglutarate, which is correct as amino acids can enter the Krebs cycle through this intermediate.
- The second option is oxaloacetic acid, which is also correct as certain amino acids can be converted into this intermediate to enter the Krebs cycle.

6. **Conclusion**: Since both alpha-ketoglutarate and oxaloacetic acid are correct entry points for amino acids into the Krebs cycle, the correct answer to the question is option C: both 1 and 2.

**Final Answer**: Proteins enter into the Krebs cycle through both alpha-ketoglutarate and oxaloacetic acid (Option C: both 1 and 2).

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