Protein amino acids are called -

Options

A. `alpha`-amino acids
B. `beta`-amino acids
C. `gamma`-amino acids
D. `sigma`-amino acids

Answer

To answer the question "Protein amino acids are called -", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Amino Acids**: Amino acids are the building blocks of proteins. Each amino acid has a specific structure that includes a central carbon atom.

2. **Identifying the Functional Groups**: The central carbon atom (also known as the alpha carbon) is attached to four different groups:
- An amino group (-NH2)
- A carboxyl group (-COOH)
- A hydrogen atom (-H)
- A variable side chain or R group that determines the identity of the amino acid.

3. **Classification of Amino Acids**: Based on the position of the amino group relative to the carboxyl group:
- If the amino group is attached to the alpha carbon (the carbon next to the carboxyl group), the amino acid is classified as an **alpha amino acid**.
- Other classifications like beta, gamma, and sigma amino acids refer to amino acids where the amino group is attached to the beta carbon, gamma carbon, and sigma carbon respectively, but these are not common in protein structure.

4. **Conclusion**: Since the amino acids that are involved in protein synthesis are primarily alpha amino acids, the correct answer to the question is that protein amino acids are called **alpha amino acids**.

### Final Answer:
Protein amino acids are called **alpha amino acids**.

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