| 1.7 Proteins |
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Summary
Key Definition Proteins are polymers of amino acids joined by covalent peptide bonds formed through dehydration synthesis between a carboxyl group and an amine group. |
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Each amino acid differs only in its R group, which can be hydrophobic, hydrophilic, or ionic. The chemical properties of these R groups drive the folding interactions that give each protein its unique shape — and therefore its unique function.
Key Definition The specific linear sequence of amino acids constitutes the primary structure, which serves as the blueprint for all higher-order folding. |
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Secondary Structure
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Arises from hydrogen bonds between backbone atoms
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Producing alpha-helices and beta-pleated sheets
Tertiary Structure
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Results from R-group interactions that fold the polypeptide into a three-dimensional shape
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Hydrogen bonds
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Hydrophobic interactions
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Ionic interactions
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Disulfide bridges
Quaternary Structure
- Forms when multiple polypeptide subunits associate into a functional complex through the same types of interactions
All four structural levels work together to determine protein function, and disruption at any level can impair or destroy biological activity.
At a Glance
| Structural Level | Bonds / Interactions | Result |
|---|---|---|
| Primary structure | Covalent peptide bonds | Specific linear sequence of amino acids |
| Secondary structure | Hydrogen bonds between backbone atoms | Alpha-helices and beta-pleated sheets |
| Tertiary structure | Hydrogen bonds, hydrophobic interactions, ionic interactions, and disulfide bridges | Three-dimensional shape |
| Quaternary structure | The same types of interactions | Multiple polypeptide subunits associate into a functional complex |