22) A protein that contains more isoleucine, phenylalanine and leucine than asparagine, lysine and
arginine is most likely
D) low on the hydropathy index scale.
23) A sequence of amino
61) A hydrated potassium ion is surrounded by a shell of water molecules oriented primarily with
their oxygen atoms toward the potassium ion.
62) In the detergent, sodium dodecyl sulfate, the sulfate groups are very hydrophob
5) Amino acids with non-ionizable side chains are zwitterions when they are _.
A) in any solution
B) at physiological pH, pH = 7.4
C) in acidic solutions only
D) in alkaline solutions only
E) All of the above
6) Glycine is not a
32) The pH inside cells is normally near pH 7. At pH 7 which statement is true about the charges
(ionization state) of the -Carboxyland -Amino groups of an amino acid?
A) The -Carboxyl group is 1- and the -Amino group is 1+.
B) The -Carboxyl group is 1+ a
11) NMR is often used for the determination of the _ of proteins.
A) molecular weight
B) isoelectric point
C) tertiary structure
12) Which is evidence that structures for proteins determined by X-ray crystallography repre
26) Which is true about hydrogen bonding for biological molecules?
A) Hydrogen bonds are strong enough to confer structural stability, for example in DNA.
B) Hydrogen bonds are weak enough to be easily broken (weaker than covalent bonds).
C) They contribu
28) Which is true about the side chains of residues in an -helix?
A) They extend above or below the pleats.
B) They extend radially outward from the helix axis.
C) They point toward the center of the helix.
D) They hydrogen bond extensively with each othe
19) What feature does a Ramachandran plot display?
A) allowed angles of phi and psi for a polypeptide backbone
B) preferred amino acids in an -helix
C) the hydropathy of amino acids
D) the variation of pH versus volume of base added during titration to de
49) In a biochemistry laboratory a student added ammonium sulfate to a tube containing a
buffered protein solution. The student then centrifuged the solution. What was the student
probably trying to do?
A) change the pH of the buffer solution to solubiliz
40) The primary structure of a protein describes the _.
A) number of each type of amino acid (percent composition)
B) linear sequence of amino acids
C) overall three-dimensional shape
D) and angles for each amino acid
41) The pe
57) Even though mass spectrometry has been in use for over a hundred years, it had only limited
use with proteins until the 1980s because
A) not many proteins had been discovered and purified before the 1980s.
B) it was not possible to disperse charged pr
65) What information can be gained by comparing the sequences of proteins that have the same or
similar function in different species?
A) to determine evolutionary relationships and relatedness of species
B) to determine sequences that are conserved among
79) The buffering capacity of a weak acid and its conjugate base is strongest when the pH = pKa .
80) Synthetic compounds used as buffers are not as valuable for experiments as naturally
occurring compounds used as buffers.
82) The liquid that emerges from the bottom of a chromatographic column is called the
83) The twenty standard amino acids are the only amino acids found in living organisms.
1) Which pair represents different conformations?
A) cis-1,2-dichloroethene and trans-1,2-dichloroethene
B) L-glycine and D-glycine
C) eclipsed ethane and staggered ethane
D) pentane and 2-methylbut
34) The ion-product constant for water, Kw, is
A) 1 x 10-7 M2 .
B) 1 x 10-7 M.
C) 1 x 10-14 M2 .
D) 1 x 10-14 M.
35) In pure water hydronium ions are formed by _ attack of oxygen on a proton in an
adjacent water molecule.
13) Concentrations of some proteins cannot be estimated by UV spectrophotometry because they
A) high in non-absorbing amino acids.
B) low in tryptophan and tyrosine.
C) low in protein.
D) high in aromatic amino acids.
43) The pH of a 10-4 M solution of HCl is
E) greater than 4.5.
44) Compare solution A with pH = 4 to solution B with pH = 6.
A) The concentration of hydronium ion in solution A is twice that in soluti
51) Since HCl is a strong acid its value of Ka is _.
A) effectively equal to infinity
B) equal to Kw
D) dependent on the concentration of HCl
52) For a weak acid with a pKa = 6.5, the effective buffering range is usually
37) Protein subunits in a multisubunit protein are held to each other primarily by
A) covalent bonds.
B) hydrophobic interactions exclusively.
C) both strong and weak interactions.
D) hydrophobic and other weak interactions.
E) All of the above