Amino acids can be acidic, basic or neutral.

Explanation

**Step-by-Step Solution:**

1. **Understanding Amino Acids**: Amino acids are organic compounds that serve as the building blocks of proteins. Each amino acid has a central carbon atom bonded to four different groups: a hydrogen atom, an amino group (-NH2), a carboxyl group (-COOH), and a variable R group (side chain).

2. **Classification of Amino Acids**: Amino acids can be classified based on the nature of their R group. The R group determines the chemical and physical properties of the amino acid, which in turn influences whether the amino acid is acidic, basic, or neutral.

3. **Acidic Amino Acids**: Amino acids that have an additional carboxyl group in their structure are classified as acidic. An example of an acidic amino acid is Glutamic Acid, which has two carboxyl groups.

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