Amino acid

Amino acids are organic molecules that serve as the building blocks for proteins. Comprising a central carbon atom to which an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a unique side chain (often referred to as an "R" group) are bonded, these compounds play a critical role in various biological processes.

Alpha-amino-acid-general-2D-stereo

Characteristics

Amino_acid_biosynthesis_overview

Amino acids have a general structure which consists of a central carbon atom (alpha carbon) bonded to an amino group, a carboxyl group, a hydrogen atom, and a distinct side chain. The properties and activities of each amino acid are determined by its specific side chain.

Classification

Amino acids can be categorized based on various criteria, including their side chain properties, nutritional requirements, and metabolic fate.

By Side Chain Properties

• Nonpolar (hydrophobic): Include alanine, valine, leucine, and isoleucine.
• Polar (hydrophilic): Include serine, threonine, and asparagine.
• Acidic: Include aspartate and glutamate.
• Basic: Include lysine, arginine, and histidine.

By Nutritional Requirements

• Essential amino acids: Cannot be synthesized by the human body and must be obtained from the diet. Examples include lysine, leucine, and valine.
• Non-essential amino acids: Can be synthesized by the human body. Examples include glycine, alanine, and serine.
• Conditionally essential amino acids: Typically non-essential, but under certain circumstances (e.g., disease or stress), their synthesis may be limited. Examples include arginine, cysteine, and glutamine.

Functions

Amino acids have numerous roles in the body:

• Protein Synthesis: They join together to form peptides and proteins.
• Neurotransmitter Synthesis: Amino acids like tryptophan and tyrosine are precursors to neurotransmitters serotonin and dopamine, respectively.
• Energy Production: Some can be metabolized to produce energy.
• Hormone Production: Certain hormones are derived from amino acids, like thyroxine from tyrosine.

Dietary Sources

Amino acids are commonly found in various foods, especially:

• Meat
• Poultry
• Fish
• Eggs
• Dairy products
• Certain grains and legumes

Deficiency

A deficiency in essential amino acids can lead to a variety of health issues, including muscle loss, weakened immune function, and growth retardation in children.

See Also

• Protein metabolism
• Enzyme
• Genetic code

Amino acid Resources
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