Amino-acid residues and peptide linkages
The peptide backbone and variable side chains are different parts of protein structure.
Key knowledge
The usual protein amino-acid building blocks have an alpha carbon associated with an amino group, a carboxyl group, hydrogen and a variable side chain. A peptide linkage connects a residue's carbonyl carbon to another residue's nitrogen, producing a polypeptide backbone. Sequence specifies the order of residues; side-chain chemistry influences interactions and folding. A linear unmodified chain has an amino end and a carboxyl end, conventionally called N and C termini.
Conditions and scope
- Ionization depends on pH; proline's nitrogen is part of a ring, and glycine has hydrogen as its side chain.
- This describes the usual peptide backbone. Terminal modification, chain cyclization and post-translational chemistry require their own descriptions.
Sources · 3
References
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Evidence and review
Alpha-amino-acid side chains, the peptide linkage and bounded polypeptide directionality.
2026-10-10 · Independent Mathematics and Information editor (AI editorial/source review; not the Chemistry/Biology/Earth author). The specified introductory inventory has no unresolved demonstrated material gap after the changes and body-based reuse. Existing advanced references retain their historical scoped approvals. English-only reference prose and explicit Lithuanian-translation-pending status are preserved.
Foundational review
2026-10-10 · Independent AI editorial inspection of this new compact reference entry, its equations, applicability, sources and knowledge connections.
Sources from other places
Agreement within this scope
Alpha-amino-acid groups and peptide-linked polypeptide chains.
Sequence and side-chain chemistry are distinct from a folded structure.
NCERT
- Biology XI: Biomolecules IndiaEnglish
§9.1, printed pp105–106: amino acids, fatty acids and glycerides; §9.3–9.6, printed pp108–111: polymers, proteins, carbohydrates and nucleotides; §9.8.2–9.8.4, printed pp114–116: active site, induced fit and conditions; §9.8.5, printed p117: hydrolysis examples
- Biology XI: Biomolecules
Entry details
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- foundation-bio-amino-acid-peptide
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- foundations-audit.1
- Structured reference record
- Foundational core completion