Which of the following statements is correct?
peptide bonds are essentially planar, with no rotation about the C—N axis.
Which of the following pairs of bonds within a peptide backbone show free rotation around both bonds?
Cα—C and N—Cα
In the alpha helix the hydrogen bonds:
are roughly parallel to the axis of the helix.
A naturally occurring hindrance to the formation of α helix is the presence of:
a Pro residue.
Amino acid residues commonly found in the middle of beta turn are:
Pro and Gly.
Experiments on denaturation and renaturation of the enzyme ribonuclease (RNase) have shown that:
the primary sequence of RNase is sufficient to determine its specific secondary and tertiary structure.
Of the 20 standard amino acids, only ______ is not optically active. The reason is that its side chain _____.
glycine; is a hydrogen atom
Two amino acids of the standard 20 contain sulfur atoms. They are:
methionine and cysteine.
The peptide alanylglutamylglycylalanylleucine has:
four peptide bonds.
By adding SDS (sodium dodecyl sulfate) during the electrophoresis of proteins, it is possible to:
separate proteins exclusively on the basis of molecular weight.
To determine the isoelectric point of a protein, first establish that a gel:
exhibits a stable pH gradient when ampholytes become distributed in an electric field.
Which amino acids contain aliphatic hydroxyl groups?
serine and threonine
The term “proteome” has been used to describe:
the complement of proteins encoded by an organism’s DNA.
Which of the following plays a role in the degradation of proteins?
An allosteric interaction between a ligand and a protein is one in which:
binding of a molecule to a binding site affects binding properties of another site on the protein.
Hydrophobic interactions make important energetic contributions to:
binding of a hormone to its receptor protein, enzyme-substrate interactions, membrane structure, three-dimensional folding of a polypeptide chain
Misfolding of polypeptides is a serious problem in cells. Which of the following diseases are associated with an accumulation of misfolded polypeptides?
Alzheimer’s and Parkinson’s only
In sickle-cell disease, as a result of a single amino acid change, the mutant hemoglobin tetramers associate with each other and assemble into large fibers. Based on this information alone, we can conclude that sickle-cell hemoglobin exhibits:
altered primary structure and altered quaternary structure; the secondary and tertiary structures may or may not be altered.
What aspects of protein structure are stabilized or assisted by hydrogen bonds?
secondary, tertiary, and quaternary structures, but not primary structure