Amino acids

Amino acids are organic compounds that combine to form proteins. They are typically composed of an amine group (−NH₂), a carboxyl group (−COOH), and a side chain (R group) that is specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, although other elements are found in the side chains of certain amino acids.

Structure

Amino acids have a central carbon atom (the α-carbon) to which the amine group, carboxyl group, hydrogen atom, and R group (side chain) are attached. The side chain determines the unique characteristics and functions of each amino acid. There are 20 standard amino acids that are encoded by the genetic code.

Classification

Amino acids can be classified based on the properties of their side chains:

• Nonpolar (hydrophobic) amino acids: e.g., alanine, valine, leucine, isoleucine, methionine, phenylalanine, tryptophan, proline
• Polar (hydrophilic) amino acids: e.g., serine, threonine, cysteine, tyrosine, asparagine, glutamine
• Acidic amino acids: e.g., aspartic acid, glutamic acid
• Basic amino acids: e.g., lysine, arginine, histidine

Essential and Non-Essential Amino Acids

Amino acids are also categorized as essential or non-essential:

• Essential amino acids cannot be synthesized by the human body and must be obtained from the diet. These include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
• Non-essential amino acids can be synthesized by the human body. These include alanine, asparagine, aspartic acid, glutamic acid, serine, and others.

Functions

Amino acids play several critical roles in the body:

• They are the building blocks of proteins, which are essential for the structure, function, and regulation of the body's tissues and organs.
• They are involved in the synthesis of hormones and neurotransmitters.
• They participate in metabolic pathways and are precursors to other important biomolecules.

Metabolism

Amino acid metabolism involves the breakdown and synthesis of amino acids. The urea cycle is a key pathway in the metabolism of amino acids, where excess nitrogen is converted to urea and excreted from the body.

Related Pages

• Protein
• Peptide
• Enzyme
• Metabolism
• Genetic code
• Hormone
• Neurotransmitter

See Also

• Biochemistry
• Molecular biology
• Nutrition