Advanced Topic 984 of 1102 Biochemistry, Environment & Industry

Alpha Helix and Beta Sheet

Common secondary structures stabilized by hydrogen bonds.

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In-depth explanation of Alpha Helix and Beta Sheet

Alpha helices and beta sheets are the two most common secondary structures, and both are stabilised by hydrogen bonds along the polypeptide backbone. In an alpha helix the chain coils into a right-handed spiral with about 3.6 residues per turn, and each C=O group hydrogen-bonds to the N-H group four residues further along. Beta sheets consist of extended strands lying side by side, with hydrogen bonds between neighbouring strands in either a parallel or an antiparallel arrangement. Side chains point outward from the helix or alternate above and below the sheet, which affects how the structure packs and binds other molecules. The allowed backbone angles for each structure are visualised with a Ramachandran plot.

Going deeper: Alpha Helix and Beta Sheet

Key ideas: The alpha helix has 3.6 residues per turn and a pitch of 5.4 angstrom, with hydrogen bonds between C=O of residue n and N-H of residue n+4, side chains pointing outward. Beta sheets align strands side by side with hydrogen bonds between strands, parallel or antiparallel. Proline breaks helices because it has no N-H and a rigid ring.

Common mistakes and connections: Students place the hydrogen bonds between side chains, but they are between backbone atoms. Another error is thinking secondary structure needs the whole protein; it is local. Silk fibroin is mostly beta sheet, keratin alpha helix. Links to tertiary folding and Ramachandran angles.

Visualization of Alpha Helix and Beta Sheet

An alpha helix compacts the chain to 1.5 angstroms per residue with 3.6 residues per turn, while an extended beta strand advances about 3.4 angstroms per residue. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Silk fibroin is rich in beta sheets, while hair keratin is mostly alpha helix.

Frequently asked questions about Alpha Helix and Beta Sheet

What is Alpha Helix and Beta Sheet?

Common secondary structures stabilized by hydrogen bonds.

Is Alpha Helix and Beta Sheet a beginner, intermediate or advanced topic?

Alpha Helix and Beta Sheet is a advanced topic in Biochemistry, Environment & Industry. It builds on beginner and intermediate topics, so review those first if needed.

What should I learn before Alpha Helix and Beta Sheet?

Study these earlier topics in Biochemistry, Environment & Industry first: Cellulose, Glycogen, Protein Structure Levels.

What comes after Alpha Helix and Beta Sheet?

The next topics in Biochemistry, Environment & Industry are Denaturation and Essential Amino Acids.

Can I practise Alpha Helix and Beta Sheet with quizzes?

Yes. The interactive lesson includes a self-check question on Alpha Helix and Beta Sheet, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.

Where Alpha Helix and Beta Sheet fits in Biochemistry, Environment & Industry

Alpha Helix and Beta Sheet is topic 9 of 127 in Biochemistry, Environment & Industry.