Amino acids are the building blocks of proteins and play crucial roles in countless biochemical processes. Here are some examples of amino acids, categorized for clarity:
Acidic (Negatively Charged) Amino Acids
These amino acids have a net negative charge at physiological pH.
- Aspartic Acid (Aspartate): Involved in the urea cycle and neurotransmission.
- Glutamic Acid (Glutamate): The most abundant excitatory neurotransmitter in the vertebrate nervous system; also involved in metabolic pathways.
Basic (Positively Charged) Amino Acids
These amino acids have a net positive charge at physiological pH.
- Lysine: Essential amino acid; important for protein synthesis and modification.
- Arginine: Involved in the urea cycle; precursor to nitric oxide.
- Histidine: Can be positively charged or neutral at physiological pH, often found in enzyme active sites due to its ability to act as both a proton donor and acceptor.
Nonpolar (Hydrophobic) Amino Acids
These amino acids tend to cluster together within proteins, away from water.
- Alanine: Simple amino acid commonly found in proteins.
- Valine: Branched-chain amino acid; essential for humans.
- Leucine: Branched-chain amino acid; essential for humans.
- Isoleucine: Branched-chain amino acid; essential for humans.
- Methionine: Contains sulfur; important for initiation of translation and as a methyl group donor.
- Phenylalanine: Aromatic amino acid; precursor to tyrosine.
- Tryptophan: Aromatic amino acid; precursor to serotonin and melatonin.
- Proline: Unique cyclic structure; often found in turns of protein structure.
- Glycine: The smallest amino acid; often found in flexible regions of proteins.
Polar (Uncharged) Amino Acids
These amino acids have polar side chains but are not charged at physiological pH.
- Serine: Contains a hydroxyl group; site for phosphorylation.
- Threonine: Contains a hydroxyl group; site for phosphorylation and glycosylation.
- Cysteine: Contains a thiol group; can form disulfide bonds.
- Tyrosine: Aromatic amino acid; can be phosphorylated.
- Asparagine: Amide derivative of aspartic acid.
- Glutamine: Amide derivative of glutamic acid.
These examples represent a diverse group of amino acids, each with unique chemical properties that contribute to the structure and function of proteins. Understanding these properties is essential for comprehending biochemical processes.
