BRAINCAKEHydrogen Bonding
A hydrogen bond is a weak attraction between a slightly positive (δ+) hydrogen atom that is covalently bonded to an electronegative atom (O or N) and a slightly negative (δ−) O or N atom nearby. In proteins, hydrogen bonds are one of the main forces that hold the chain in its folded shape.
In the polypeptide backbone. Every peptide bond contains a C=O group (the O is δ−) and an N–H group (the H is δ+). Hydrogen bonds between these groups in different parts of the chain produce the secondary structure:
• In an α-helix, the chain coils, and the C=O of each amino acid forms a hydrogen bond with the N–H of the amino acid four places further along.
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Key terms in this lesson
- tertiary structure
- The overall three-dimensional shape formed by further folding of a polypeptide chain, held by bonds between R groups.
- denaturation
- A permanent change to the tertiary or secondary structure of a protein, caused by heat or extreme pH, that destroys its shape and function.
More in Biological Molecules
- Phospholipids
- Unit Membrane
- Test for Lipids
- Amino-acids
- Disulfide Bridges
- Ionic Bonds
- Protein Structure
- Globular Proteins
All 25 lessons in Biological Molecules · All Edexcel AS-level Biology topics