The building blocks of proteins are amino acids. Amino acids are small organic molecules consisting of a central alpha (α) carbon atom bonded to an amino group (NH2), a carboxyl group (COOH), a hydrogen atom, and a variable side chain (R group) that differs among amino acids
. Proteins are formed by linking multiple amino acids together through peptide bonds, which connect the amino group of one amino acid to the carboxyl group of another, creating long chains that fold into functional proteins
. There are 20 standard amino acids that make up proteins, categorized as essential, non-essential, and semi-essential based on whether the body can synthesize them or if they must be obtained from the diet. Nine of these amino acids, including histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine, are essential because they cannot be synthesized by humans and must be consumed through food
. In summary:
- Proteins are polymers made of amino acid monomers.
- Each amino acid has a central carbon linked to an amino group, carboxyl group, hydrogen, and a unique side chain.
- Amino acids are joined by peptide bonds to form protein chains.
- There are 20 amino acids involved in protein synthesis, with 9 classified as essential
This molecular composition and linkage define the primary structure of proteins, which further fold into complex shapes to perform biological functions.
