Deck 6: The Three-Dimensional Structure of Proteins

Question 1

The amino acid side chain residues in an α helix point outwards away from the center of the helix.

Answer 1

True

Question 2

Protein folding is a thermodynamically favorable process under physiological conditions because:

A) there is an increase in entropy associated with protein folding.
B) there is a decrease in entropy of the solvent by burying hydrophobic groups within the molecule.
C) of the large negative enthalpy change associated with many noncovalent interactions.
D) no intermediate stage disulphide bonds form during the folding process.
E) all of the above.

Answer 2

C

Question 3

Which of the following statements about α-keratins is FALSE?

A) They include a major class of protein that comprises hair, fingernails and animal skin.
B) Individual molecules are α-helical.
C) There is a strip of contiguous hydrophobic surface making a shallow spiral around the helix.
D) They include a small globular regions covalently linked to the surface.
E) Pairs of α-helices twist about each other in a coiled-coil structure held together entirely by hydrophobic interactions.

Answer 3

E

Question 4

In considering protein secondary structure which of the following is INCORRECT?

A) An α helix repeats after 18 residues and has 3.6 residues per turn.
B) A network of main-chain hydrogen bonds connect β strands in a β sheet.
C) The most common structures are the α helix and the β sheet.
D) The 310 helix is right-handed and often contains proline residues.
E) The β strands can be in either parallel or antiparallel configuration.

Question 5

The cavity in the GroEL-GroES complex from E. coli provides a favorable environment that prevents ________ and mis-folding.

Question 6

Which of the following is CORRECT when considering the tertiary structure of globular proteins?

A) β sheets are usually twisted or wrapped into barrel structures.
B) Hydrophobic residues are normally on the inside and hydrophilic residues are on the outside.
C) The amino acid proline never occurs in a region where the polypeptide chain bends or turns.
D) All parts of the proteins can be classified as helix, β sheet or turns.
E) None of the above.

Question 7

The folded conformation of proteins can be stabilized by the binding of a metal ion or cofactor.

Question 8

A ________ plot describes which structures in a polypeptide are sterically possible and which are not based on the angles of rotation about the backbone Namide -Cα and Cα-Ccarbonyl bonds.

Question 9

Scurvy results in weakness in collagen fibres because the enzymes that catalyze ________ of proline and lysine residues in collagen require Vitamin C.

Question 10

Proteins have an asymmetrical tertiary structure, while multisubunit proteins can exhibit several types of symmetry.

Question 11

Bovine spongiform encephalopathy is an infectious disease caused by a prion protein, which undergoes a ________ change to become pathogenic.

Question 12

Which technique is able to investigate secondary structural features of proteins?

A) Infrared spectroscopy
B) Ultraviolet spectroscopy
C) Fluorescence spectroscopy
D) Circular dichroism
E) All of the above

Question 13

The interactions that stabilize multisubunit complexes are different to those that stabilize tertiary structure.

Question 14

The protein that makes up about a third of the total protein mass in animals is:

A) β-keratin.
B) collagen.
C) hemoglobin.
D) myoglobin.
E) α-keratin.

Question 15

________ between amide protons and carbonyl oxygens is necessary to stabilize a regular folding of protein secondary structure.

Question 16

Proteins cannot self-assemble into a functional conformation after they have been denatured.

Question 17

Fibroin is a β-sheet protein, with a high proportion of glycine.

Question 18

The functional organization of proteins where specific complexes of two or more polypeptides are formed is called ________ structure.

Question 19

Tropocollagen is a double helix of two left-handed polypeptide chains.

Question 20

Protein folding is a random process, whereby a vast number of possible conformations are tested to find the desired most stable state.

Question 21

________ spectroscopy can be used to study dynamic processes in solution.

Question 22

SDS gel electrophoresis can be used to determine:

A) whether subunits in a protein complex are identical or not.
B) the molecular mass of a native protein complex.
C) the overall charge on a polypeptide.
D) the molecular mass of denatured protein subunits.
E) none of the above.