BRAINCAKETertiary Structure of Proteins
The tertiary structure is the overall three-dimensional shape formed when the coiled or folded chain folds further. It is held in place mainly by interactions between the side chains (R groups):
• Disulfide bridges: cysteine has the side chain -CH2SH. Two cysteine -SH groups, which may be far apart in the sequence, can be oxidised to form a covalent sulfur-sulfur bond, -CH2-S-S-CH2-. These are the strongest links.
• Ionic interactions: an acidic side chain present as -COO− attracts a basic side chain present as -NH3+.
• Hydrogen bonds: between polar side chains, for example -OH groups (as in serine).
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All 15 lessons in Amino Acids, Proteins and DNA · All AQA A-level Chemistry topics