Α-amino acid

Overview

Α-amino acids are organic compounds that contain both an amino group (−NH₂) and a carboxyl group (−COOH) attached to the same carbon atom, known as the α-carbon. These molecules are the building blocks of proteins, which are essential macromolecules in all living organisms. The general formula for an α-amino acid is RCH(NH₂)COOH, where R represents a side chain specific to each amino acid.

Structure

The α-carbon in α-amino acids is typically a chiral center, meaning it has four different groups attached to it: the amino group, the carboxyl group, a hydrogen atom, and a variable side chain (R group). This chirality results in two possible stereoisomers, L- and D-forms, with L-amino acids being the predominant form found in proteins.

Side Chains

The side chain (R group) of an α-amino acid determines its properties and role in proteins. Side chains can be nonpolar, polar, acidic, or basic, influencing the amino acid's solubility, reactivity, and interaction with other molecules.

Biological Importance

Α-amino acids are crucial for life, as they are the monomers that polymerize to form proteins. Proteins perform a vast array of functions, including catalyzing biochemical reactions (enzymes), providing structural support (collagen), and regulating biological processes (hormones).

Protein Synthesis

During protein synthesis, α-amino acids are linked together by peptide bonds in a specific sequence dictated by the genetic code. This sequence determines the protein's three-dimensional structure and function.

Types of Α-amino acids

There are 20 standard α-amino acids encoded by the universal genetic code. These include:

• Glycine
• Alanine
• Valine
• Leucine
• Isoleucine
• Phenylalanine
• Tyrosine
• Tryptophan
• Serine
• Threonine
• Cysteine
• Methionine
• Aspartic acid
• Glutamic acid
• Asparagine
• Glutamine
• Lysine
• Arginine
• Histidine
• Proline

Synthesis and Metabolism

Α-amino acids can be synthesized in the body or obtained from the diet. Essential amino acids cannot be synthesized by the body and must be obtained from food. Non-essential amino acids can be synthesized from other compounds in the body.

Metabolic Pathways

Amino acids are involved in various metabolic pathways, including the synthesis of neurotransmitters, hormones, and other nitrogen-containing compounds. They can also be converted into glucose or fatty acids for energy storage.

Also see

• Protein
• Peptide bond
• Chirality (chemistry)
• Essential amino acid
• Non-essential amino acid