1. Biological Functions in Organisms

• Protein Synthesis: Serve as the “building blocks” for polypeptide chains and proteins, enabling the assembly of structural proteins (e.g., collagen), enzymes, antibodies, and signaling molecules (e.g., hormones like insulin).
• Neurotransmission & Signal Transduction: Some amino acids act as neurotransmitters or precursors. For example:
  • Glutamate is the main excitatory neurotransmitter in the brain.
  • Glycine functions as an inhibitory neurotransmitter.
  • Tryptophan is a precursor to serotonin (regulates mood and sleep), and tyrosine is a precursor to dopamine and adrenaline (involved in stress responses and reward pathways).
• Energy Production: During metabolic stress (e.g., fasting), amino acids (e.g., alanine) can be broken down via gluconeogenesis to produce glucose for energy.
• Nitrogen Metabolism: Participate in nitrogen transport and recycling. For instance, glutamine acts as a major carrier of nitrogen in the bloodstream, supporting cell growth (especially in the gut and immune cells).
• Antioxidant Defense: Cysteine is a component of glutathione, a key antioxidant that protects cells from oxidative damage.
• pH Regulation: The amino and carboxyl groups in amino acids can act as buffers, helping maintain cellular and bodily fluid pH balance.

2. Applications in Industries

• Nutrition & Supplements:
  • Used in dietary supplements to address deficiencies (e.g., lysine in vegetarian diets, which is limited in plant-based foods).
  • Added to sports nutrition products (e.g., branched-chain amino acids, BCAAs: leucine, isoleucine, valine) to support muscle repair and reduce fatigue.
• Agriculture & Animal Feed:
  • Added to livestock and poultry feed to optimize growth and health. For example, methionine and lysine are often supplemented in grain-based feeds (which are naturally low in these amino acids) to enhance protein synthesis in animals.
• Pharmaceuticals:
  • Used as active ingredients or precursors in drugs. For example:
    • L-dopa (a derivative of tyrosine) treats Parkinson’s disease.
    • Glutamine supplements aid in recovery from surgeries or intestinal disorders.
• Food Industry:
  • Serve as flavor enhancers (e.g., monosodium glutamate, MSG, derived from glutamic acid) or preservatives.
  • Added to functional foods (e.g., infant formula) to ensure balanced amino acid profiles.
• Cosmetics:
  • Incorporated into skincare products for their role in collagen synthesis (e.g., proline, glycine) or antioxidant effects (e.g., cysteine).