Chapter 6 - Key Concepts & Review Points

Question 1

The planar character of the peptide bond limits the ____________ of the polypeptide chain.

Answer 1

conformational flexibility

Question 2

The alpha helix and beta sheet allow the polypeptide to adopt favorable ____________.

Answer 2

dihedral angles

Question 3

Fibrous proteins contain long stretches of regular secondary structure, such as the ____________ in alpha keratin and the ____________ in collagen.

Answer 3

coiled coils

triple helix

Question 4

Not all polypeptide segments from regular secondary structure such as ____________ or ____________.

Answer 4

alpha helices

beta sheets

Question 5

X-ray crysallography and NMR spectroscopy are used to determine the positions of ____________ in proteins.

Answer 5

atoms

Question 6

Nonpolar residues tend to occur in the protein ____________ and polar residues on the ____________.

Answer 6

interior

exterior

Question 7

A protein’s tertiary structure consists of secondary structural elements that combine to form ____________ and ____________.

Answer 7

motifs

domains

Question 8

Over time, a protein’s ____________ is more highly conserved than its ____________.

Answer 8

structure

sequence

Question 9

Bioinformatics databases store ____________. Software makes it possible to visualize proteins and compare their structural features.

Answer 9

macromolecular structure coordinates

Question 10

Some proteins contain multiple ____________, usually arranged symmetrically.

Answer 10

subunits

Question 11

Protein stability depends primarily on ____________ and secondarily on ____________.

Answer 11

hydrophobic effects

electrostatic interactions

Question 12

A protein that has been denatured my undergo ____________.

Answer 12

renaturation

Question 13

Protein structures are ____________ and may include unfolded regions.

Answer 13

flexible

Question 14

A folding protein follows a pathway from ________ energy and ________ entropy to ________ energy and ________ entropy.

Answer 14

high
high
low
low

Question 15

Protein disulfide isomerase catalyzes ____________.

Answer 15

disulfide bond formation

Question 16

A variety of molecular chaperones assist protein folding via a(n) ________________ mechanism.

Answer 16

ATP-dependent bind-and-release

Question 17

Amyloid diseases result from ____________.

Answer 17

protein misfolding

Question 18

The misfolded proteins form fibrils containing extensive ____________.

Answer 18

beta structure

Question 19

________ levels of structural complexity are used to describe the three-dimensional shapes of proteins.

Answer 19

four

Question 20

The conformational flexibility of the peptide group is described by its ____________.

Answer 20

dihedral angles (or phi and psi torsion angles)

Question 21

The alpha helix is a regular secondary structure in which hydrogen bonds form between backbone groups ________ residues apart. In the beta sheet, hydrogen bonds form between ________________.

Answer 21

four

backbones of separate polypeptide segments

Question 22

Fibrous proteins are characterized by a single type of ____________ structure: alpha keratin is a ____-handed coil of ________ alpha helices, and collagen is a ____-handed triple helix with ________ residues per turn.

Answer 22

secondary
left
two
left
three

Question 23

The structures of proteins have been determined mainly by ____________ and ____________.

Answer 23

x-ray crystallography

NMR spectroscopy

Question 24

The nonpolar side chains of a globular protein tend to occupy the protein’s ____________; the polar side chains tend to define its ____________.

Answer 24

interior

surface

Question 25

Protein structures can be classified on the basis of ____________, ____________, ____________, or ____________. Structural elements are more likely to be evolutionarily conserved than are amino acid sequences.

Answer 25

motifs
secondary structure content
topology
domain architecture

Question 26

Structural bioinformatic is concerned with the ____________, ____________, ____________, and ____________ of macromolecular structures.

Answer 26

storage
visualization
analysis
comparison

Question 27

The indiviual subunits of multisubunit proteins are usually ____________ arranged.

Answer 27

symmetrically

Question 28

____________ protein structures are only slightly more stable than their ____________ forms. The ____________ is the primary determinant of protein stability. ____________ and ____________ contribute relatively little to a protein’s stability.

Answer 28

native
denatured
hydrophobic effect
hydrogen bonding
ion pairing

Question 29

Studies of protein denaturation and renaturation indicate that the ____________ of a protein determines its three-dimensional structure.

Answer 29

primary structure

Question 30

Proteins fold to their native conformations via ____________ in which small elements of structure coalesce into larger structures.

Answer 30

direct pathways

Question 31

____________ facilitate protein folding in vivo by repeatedly binding and releasing a polypeptide in a(n) ____________ manner and providing it with a(n) ____________ in which to fold.

Answer 31

molecular chaperones
ATP-dependent
isolated environment

Question 32

Diseases caused by protein misfolding include the ____________, ____________, and the ____________.

Answer 32

amyloidoses
Alzheimer’s disease
transmissible spongiform encephalopathies (TSEs)