The acidic amino acids are those with side chains that have a net negative charge at physiological pH.
Acidic Amino Acids Explained
Amino acids are the building blocks of proteins. They have a basic structure consisting of an amino group, a carboxyl group, and a side chain, all attached to a central carbon atom. The side chain is the variable part that gives each amino acid its unique properties.
Identifying Acidic Amino Acids
According to the provided reference, two amino acids possess acidic side chains at neutral pH:
- Aspartic acid (Asp), also known as aspartate in its ionized form.
- Glutamic acid (Glu), also known as glutamate in its ionized form.
These amino acids have carboxyl groups (-COOH) in their side chains which can lose a proton (H⁺) to become negatively charged carboxylate groups (-COO⁻) at physiological pH. The ability to donate protons classifies them as acidic.
Table of Acidic Amino Acids
| Amino Acid | Three-Letter Abbreviation | One-Letter Abbreviation | Side Chain |
|---|---|---|---|
| Aspartic Acid | Asp | D | -CH₂COOH (becomes -CH₂COO⁻ at neutral pH) |
| Glutamic Acid | Glu | E | -CH₂CH₂COOH (becomes -CH₂CH₂COO⁻ at neutral pH) |
Significance of Acidic Amino Acids
- Protein Structure: These amino acids contribute to the overall 3D structure of proteins. They can form ionic bonds and hydrogen bonds with other charged or polar amino acids.
- Enzyme Catalysis: The carboxylate groups in aspartate and glutamate can participate in catalytic mechanisms in enzymes.
- Buffering Capacity: They can act as buffers to help maintain pH levels in cells.
- Ion Transport: They play crucial roles in transporting ions across cellular membranes.
Conclusion
Aspartic acid (Asp) and glutamic acid (Glu) are the two primary examples of acidic amino acids because they have side chains containing carboxyl groups, which are negatively charged at physiological pH. This acidity is vital for their role in protein structure and function.
