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8 years ago
Many of the most important interactions in biology involve non-covalent interactions, such as ionic bonds,
hydrogen bonds, hydrophobic interactions, and van der Waals interactions. Explain protein secondary structure, tertiary structure, and quaternary structure in terms of these non-covalent interactions.
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8 years ago Edited: 8 years ago, bio_man
Explain protein secondary structure, tertiary structure, and quaternary structure in terms of these non-covalent interactions.

Intramolecular noncovalent interactions are largely responsible for the secondary and tertiary structure of proteins and therefore the protein's function in the mechanisms of life. Intermolecular noncovalent interactions are responsible for protein complexes (quaternary structure) where two or more proteins function in a coherent mechanism.

Secondary structure = local folding of residues into regular patterns

- In the alpha-helix, the carbonyl oxygen of the first amino acid residue forms a hydrogen bond with the amide of residue the fourth amino acid residue.
- Although each hydrogen bond is relatively weak in isolation, the sum of the hydrogen bonds in a helix makes it quite stable.
- In a beta-sheet, carbonyl oxygens and amides form hydrogen bonds.
- These secondary structures can be either antiparallel or parallel and need not be planar but can be twisted. See attachment one for further details.

The tertiary structure is held together by the following (see attachment 2):

Hydrophobic interactions
• Electrostatic interactions
– Salt bridges
• Hydrogen bonds
• Covalent bonds
– Disulfide bridges
• Extracellular proteins
• Hydration
– flexibility

These bonds are formed between the R-groups of the amino acids in the protein, and so depends on what the sequence of amino acids.

The quaternary structure is held together by ionic, hydrogen, and disulfide bonds between amino acids of different peptides. This makes up a polypeptide (poly meaning many). The individual peptide chains are usually globular, but can arrange themselves into a variety of quaternary shapes. Example: Hemoglobin, the oxygen-carrying protein in red blood cells, consists of four globular subunits arranged in a tetrahedral (pyramid) structure.

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8 years ago
Tell me if your need further clarification!
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8 years ago
thank you so much for the help!
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