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Questions and Answers
What type of forces favor protein folding between oppositely charged R-groups?
Which type of forces involve interactions among induced dipoles that arise from fluctuations in charge densities?
What type of bond gives shape to the secondary structure of proteins?
Which force occurs when uncharged non-bonded atoms come very close together but do not induce dipoles?
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Which type of interaction involves the ionized R-groups of amino acids with the dipole of the water molecule?
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How do parts of amino acid chains stabilize the tertiary shape through covalent bonding?
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What type of bonds are formed between -NH, + and -COO- groups in proteins?
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Which type of protein structure has hydrophobic parts towards the center and hydrophilic parts towards the edges?
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Which protein structure consists of repeated sequences of amino acids and is insoluble in water?
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What is the function of chaperone proteins in protein folding?
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When are chaperone proteins typically expressed at elevated levels?
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What is the order followed in the folding of a newly synthesized polypeptide into its secondary structure?
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Study Notes
Forces Controlling Protein Structures
- Three types of electrostatic forces control protein structures:
- Charge-charge interactions between oppositely charged R-groups
- Charge-dipole interactions between ionized R-groups and water molecules
- Dipole-dipole interactions between polar R-groups and water molecules
Van der Waals Forces
- Attractive van der Waals forces arise from interactions among induced dipoles between adjacent uncharged non-bonded atoms
- Repulsive van der Waals forces occur when uncharged non-bonded atoms come very close together but do not induce dipoles
- Disulfide (S-S) bonds contribute to the secondary structure of proteins
Tertiary Structure of Proteins
- Four ways parts of the amino acid chain interact to stabilize the tertiary shape:
- Covalent bonding (e.g., disulfide bridges)
- Hydrogen bonding between polar groups on the side chain
- Salt bridges (ionic bonds) between -NH, + and -COO- groups
- Hydrophobic/Hydrophilic interactions
- Functions of domains include binding of substrates or ligands, anchoring proteins to membranes, and interacting with regulatory molecules
Protein Types
- Globular proteins have ball-like structures with hydrophobic parts towards the center and hydrophilic parts towards the edges, making them water-soluble
- Fibrous proteins form long fibers consisting of repeated sequences of amino acids, which are insoluble in water
Quaternary Structure
- Quaternary structure refers to the arrangement of multiple polypeptide chains in a protein
- Factors that facilitate folding and refolding include:
- Native conformation of a protein being thermodynamically favored
- Folding being modular with an order of steps
- Auxiliary proteins assisting folding, such as chaperone proteins
Chaperone Proteins
- Chaperone proteins assist in folding by:
- Preventing misfolding of nascent proteins
- Acting as catalysts to increase the rates of the final stage in the folding process
- Suppressing non-productive interactions by binding to transiently exposed portions of the polypeptide chain
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Description
Test your knowledge on the maintenance of three-dimensional shape in proteins and the forces controlling protein structures, including charge-charge interactions, charge-dipole interactions, and dipole-dipole interactions. Explore the influence of electrostatic forces in protein folding and interaction with water molecules.
