Only ..................... amino acids are present in the proteins.

Explanation

**Step-by-Step Solution:**

1. **Understanding Amino Acids**: Amino acids are organic compounds that consist of an amino group (-NH2), a carboxyl group (-COOH), and a unique side chain (R group) that determines the characteristics of each amino acid.

2. **Role of Amino Acids in Proteins**: Amino acids are the building blocks of proteins. They link together through peptide bonds to form polypeptides, which then fold into functional proteins.

3. **Total Number of Amino Acids**: In nature, around 500 different amino acids have been discovered. However, not all of these are used in protein synthesis.

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