Peptide bond

A covalent amide linkage joining the carboxyl group of one amino acid to the amino group of another. Its resonance gives the linkage partial double-bond character and restricts rotation.

Peptide bond formation: A condensation reaction joins amino acids through an amide linkage, releasing water in the formal reaction. This reaction describes the chemical joining that creates the linkage.
Amino acid: An organic molecule containing amino and carboxyl groups, with a side chain that varies among its types. The peptide bond forms by joining functional groups on neighboring amino acids.
Ribosome: A ribonucleoprotein complex that translates messenger RNA into a chain of amino acids. Its peptidyl-transferase center forms peptide bonds as the chain grows.
Ester bond: A covalent linkage formed between a carboxylic acid group and an alcohol group. It is another common carbonyl-containing linkage, but it joins different functional groups.
Amide resonance: Delocalization of a nitrogen lone pair into a carbonyl group gives an amide bond partial double-bond character. Resonance accounts for the peptide bond’s rigidity and near-planarity.
Carboxyl group: A functional group consisting of a carbonyl and hydroxyl group attached to the same carbon atom. Its carbonyl carbon provides one side of the peptide linkage.
Peptidase: An enzyme that hydrolyzes peptide bonds in peptides or proteins. Peptidases cleave the linkage to digest proteins or regulate protein activity.
Glycosidic bond: A covalent bond that connects a carbohydrate’s anomeric carbon to another group, often another sugar. It links sugar units rather than amino-acid residues.
Peptide bond planarity: The atoms of a peptide group lie approximately in one plane because its C–N bond has partial double-bond character. Planarity is a direct structural consequence of the linkage’s resonance.
Amino group: A nitrogen-containing functional group, commonly written as –NH₂ or –NH₃⁺ depending on protonation. The amino group supplies the nitrogen that joins the neighboring carbonyl carbon.

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