Lecture 5 - Protein folding

Question 1

Disulfide bonds can be reversibly broken by reducing with

Answer 1

beta-mercaptoethanol

Question 2

Noncovalent bonds in a protein can be disrupted by

Answer 2

urea

Question 3

Tertiary interactions are important in determining the

Answer 3

secondary structure of proteins

Question 4

Tertiary interactions are interactions between

Answer 4

residues that are far apart in the sequence

Question 5

Protein denaturation can be observed by measuring the change in

Answer 5

optical rotation, viscosity, and UV absorption

Question 6

Proteins are denatured by

Answer 6

• Heat
• Detergents
• pH changes
• Hydrophobic organic compounds
• Salts
• Guanidinium chloride
• Urea

Question 7

How does heat denature proteins?

Answer 7

By disrupting non-covalent interactions

Question 8

How do detergents denature proteins?

Answer 8

By interfering with hydrophobic interactions

Question 9

How does pH denature proteins?

Answer 9

by altering ionization states of amino acids

Question 10

How do hydrophobic organic compounds denature proteins?

Answer 10

By interfering with hydrophobic interactions of the protein by interacting with water

Question 11

How does guanidinium chloride denature proteins?

Answer 11

By attracting to the peptide backbone and side chains and screening favorable interactions that might stabilize the protein

Question 12

How does urea denature proteins?

Answer 12

By hydrogen bonding to peptide bonds and weakening intermolecular bonds and interactions, weakening the overall secondary and tertiary structure

Question 13

Proteins fold due to the energy gain of going from the

Answer 13

denatured to the folded state

Question 14

As temperature increases, ΔG

Answer 14

decreases

Question 15

The transfer of a nonpolar group from an aqueous environment to the protein’s nonpolar interior is _______ driven.

Answer 15

entropically

Question 16

A partial unfolding of the structure

Answer 16

destabilizes the remaining structure

Question 17

The essence of protein folding is the tendency to

Answer 17

retain partly correct intermediates.

Question 18

In globular proteins, the average length of an alpha helix is greater than _______ residues

Answer 18

15

Question 19

Protein folding/unfolding is not all or nothing. It takes place through

Answer 19

transient intermediates