Chapter 6 - Key Concepts & Review Points Flashcards
The planar character of the peptide bond limits the ____________ of the polypeptide chain.
conformational flexibility
The alpha helix and beta sheet allow the polypeptide to adopt favorable ____________.
dihedral angles
Fibrous proteins contain long stretches of regular secondary structure, such as the ____________ in alpha keratin and the ____________ in collagen.
coiled coils
triple helix
Not all polypeptide segments from regular secondary structure such as ____________ or ____________.
alpha helices
beta sheets
X-ray crysallography and NMR spectroscopy are used to determine the positions of ____________ in proteins.
atoms
Nonpolar residues tend to occur in the protein ____________ and polar residues on the ____________.
interior
exterior
A protein’s tertiary structure consists of secondary structural elements that combine to form ____________ and ____________.
motifs
domains
Over time, a protein’s ____________ is more highly conserved than its ____________.
structure
sequence
Bioinformatics databases store ____________. Software makes it possible to visualize proteins and compare their structural features.
macromolecular structure coordinates
Some proteins contain multiple ____________, usually arranged symmetrically.
subunits
Protein stability depends primarily on ____________ and secondarily on ____________.
hydrophobic effects
electrostatic interactions
A protein that has been denatured my undergo ____________.
renaturation
Protein structures are ____________ and may include unfolded regions.
flexible
A folding protein follows a pathway from ________ energy and ________ entropy to ________ energy and ________ entropy.
high
high
low
low
Protein disulfide isomerase catalyzes ____________.
disulfide bond formation
A variety of molecular chaperones assist protein folding via a(n) ________________ mechanism.
ATP-dependent bind-and-release
Amyloid diseases result from ____________.
protein misfolding
The misfolded proteins form fibrils containing extensive ____________.
beta structure
________ levels of structural complexity are used to describe the three-dimensional shapes of proteins.
four
The conformational flexibility of the peptide group is described by its ____________.
dihedral angles (or phi and psi torsion angles)
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 ________________.
four
backbones of separate polypeptide segments
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.
secondary left two left three
The structures of proteins have been determined mainly by ____________ and ____________.
x-ray crystallography
NMR spectroscopy
The nonpolar side chains of a globular protein tend to occupy the protein’s ____________; the polar side chains tend to define its ____________.
interior
surface
Protein structures can be classified on the basis of ____________, ____________, ____________, or ____________. Structural elements are more likely to be evolutionarily conserved than are amino acid sequences.
motifs
secondary structure content
topology
domain architecture
Structural bioinformatic is concerned with the ____________, ____________, ____________, and ____________ of macromolecular structures.
storage
visualization
analysis
comparison
The indiviual subunits of multisubunit proteins are usually ____________ arranged.
symmetrically
____________ 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.
native denatured hydrophobic effect hydrogen bonding ion pairing
Studies of protein denaturation and renaturation indicate that the ____________ of a protein determines its three-dimensional structure.
primary structure
Proteins fold to their native conformations via ____________ in which small elements of structure coalesce into larger structures.
direct pathways
____________ 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.
molecular chaperones
ATP-dependent
isolated environment
Diseases caused by protein misfolding include the ____________, ____________, and the ____________.
amyloidoses
Alzheimer’s disease
transmissible spongiform encephalopathies (TSEs)
