BIOCHEM ACS FINAL EXAM LATEST 2023-2024 REAL
EXAM 200 QUESTIONS AND DETAILED ANSWERS
(100% VERIFIED ANSWERS)|ALREADY GRADED A+
Give the one letter and three letter code for the 3 amino acids that have side chains
that can get phosphorylated.
Ser (S), Thr (T), Tyr (Y)
Which amino acid can react with itself to form a dimer by formation of a disulfide
bond?
Cys (C)
At a pH above its pKa, the phenol group of tyrosine is . A. protonated B. deprotonated At a pH above its pKa, the phenol group of tyrosine is DEPROTONATED. My Note: pH > pKa = deprotonated pH < pKa = protonated At a pH below its pKa, the side chain-amino group of lysine is .
A. protonated
B. deprotonated
At a pH below its pKa, the side chain-amino group of lysine is PROTONATED.
My Note:
pH > pKa = deprotonated
pH < pKa = protonated
Which of the following amino acids has a charged polar side chain at pH 7.0?
What is the charge?
A) Leu
B) Ala
C) Met
D) Trp
E) Glu
E) Glu
Charge is negative 1
Which of the following amino acids does not have an ionizable side chain?
A) Asp B) Cys C) Lys D) His E) Asn
E) Asn
Which of the following amino acids has an uncharged polar side chain at pH 7.0?
A) Arg
B) Thr
C) Glu
D) Pro
E) Ile
B) Thr
Which of the following tripeptides would be expected to be the most hydrophobic?
A) KYG
B) KYA
C) GYA
D) DYA
E) DYG
C) GYA
You are trying to separate five proteins, which are listed below, by gel filtration
chromatography. Rank the proteins from first to last to elute.
A) cytochrome c (12 kDa)
B) RNA polymerase (99 kDa)
C) glutamine synthetase (621 kDa)
D) interferon-γ (34 kDa)
E) hemoglobin (62 kDa)
C) glutamine synthetase (621 kDa)
B) RNA polymerase (99 kDa)
E) hemoglobin (62 kDa)
D) interferon-γ (34 kDa)
A) cytochrome c (12 kDa)
C, B, E, D, A
My Note: in gel filtration chromatography, biggest molecules elute first, smallest
molecules elute last (because the small ones get stuck in the beads so they can’t
elute as quickly).
SDS-PAGE separates proteins primarily due to differences in
A) isoelectric point.
B) mass.
C) polarity.
D) solubility.
E) amino acid sequence.
B) MASS
Which statement is true concerning the structure of proteins?
A. The primary structure is the sequence of amino acids.
B. Alpha helices and beta sheets are examples of secondary structure.
C. Side chains (R-groups) of amino acids can be hydrophilic or hydrophobic.
D. Proteins made of two or more polypeptide chains have quaternary structure.
E. All statements are true.
E. All statements are true
Proteins 1 and 2 interact strongly. A significant part of the interaction is between
the amino acid side chains shown below.
PROTEIN 1 — ARGININE
PROTEIN 2 — GLUTAMIC ACID
Assume that a mutation occurs in protein 2 that changes the amino acid shown
above to one of the amino acids shown below.
Ser, Leu, Lys, Asp
What change should disrupt the interaction between proteins 1 and 2 the most? the
least?
A. The most: aspartic acid; the least: leucine
B. The most: lysine; the least: serine
C. The most: Serine; the least: aspartic acid
D. The most: lysine; the least: aspartic acid
E. The most: aspartic acid; the least: serine
D. The most: lysine; the least: aspartic acid
Which statement below does not describe fibrous proteins?
A) Domains have a globular fold.
B) These proteins usually contain only one type of secondary structure.
C) These proteins usually exhibit structural or protective characteristics.
D) These proteins have usually elongated hydrophilic surfaces.
E) These proteins are usually insoluble in water.
A) Domains have a globular fold.
The molecular weight of a purified protein is 60 kDa as measured using gel
filtration (size exclusion). SDS-‐PAGE analysis shows two bands, alpha with a
molecular weight of 15 kDa and beta with a molecular weight of 30 kDa. The best
description for the quaternary structure of this protein is:
A. (alpha)₁(beta)₁
B. (alpha)₂(beta)₁
C. (alpha)₂(beta)₂
D. (alpha)₁(beta)₂
B. (alpha)₂(beta)₁
SDS-PAGE is carried out under denaturing conditions meaning that any quaternary
structure is destroyed by SDS and heating. The molecular weight of catalase
determined by size exclusion chromatography is 240 kDa. Compare the value you
found in question #22 and 240 kDa. What is the quaternary structure of catalase?
Tetramer
Which of the following is true regarding gel-filtration chromatography and PAGE?
A) In both, small proteins move most rapidly.
B) In both, large proteins move most rapidly.
C) In PAGE, large proteins move most rapidly but in gel filtration, small proteins