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BIOCHEM ACS Final Exam Practice Questions
with Figures and Correct Answers New Modified
Exam Currently Tested and Graded A+ 2026 Latest
A weak acid HA has a pKa of 6.78. Which of the following is true for a solution
of HA at pH 5.22?
A. Very high [HA] and essentially no [A-]
B. Higher [HA] and low [A-]
C. Equal [HA] and [A-]
D. Higher [A-] and low [HA]
<Correct Answer>>B Higher [HA] and low [A-]
My Note:
pH > pKa = deprotonated
pH < pKa = protonated
a. Give the one letter and 3 letter code for the basic amino acids.
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b. Would you expect these amino acids to be on the interior or exterior of a
globular protein?
<Correct Answer>> Lys (K), Arg (R), His (H); exterior
Glutamic acid is one of 2 acidic amino acids.
a. What is the one letter and 3 letter code for the other one?
b. What is the charge of the side chains of these 2 amino acids?
<Correct Answer>> Asp (D); negative 1
Would you expect Leu to be in the interior or exterior of a globular protein?
<Correct Answer>> Interior
My Note: Leucine is NON-POLAR
Give the one letter and three letter code for the 3 amino acids that have side
chains that can get phosphorylated.
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<Correct Answer>> Ser (S), Thr (T), Tyr (Y)
Which amino acid can react with itself to form a dimer by formation of a
disulfide bond?
<Correct Answer>> Cys (C)
At a pH above its pKa, the phenol group of tyrosine is .
A. protonated
B. deprotonated
<Correct Answer>> At a pH above its pKa, the phenol group of tyrosine is
DEPROTONATED.
My Note:
pH > pKa = deprotonated
pH < pKa = protonated
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At a pH below its pKa, the side chain-amino group of lysine is .
A. protonated
B. deprotonated
<Correct Answer>> At a pH below its pKa, the side chain-amino group of
lysine is PROTONATED.
My Note:
pH > pKa = deprotonated
pH < pKa = protonated
The correct operational relationship between pKa and pH is that:
A. both are log functions.
B. both are always <7 for acids, and >7 for bases.
C. These two concepts are not operationally related in any way since biological
fluids contains mixtures of too many acids and bases.
D. When pH = pKa , the compound in question will have a charge of +0.5.
E. When pH = pKa , the ionizable compound in question (whether acid or base)
will be half protonated and half deprotonated.
<Correct Answer>> E. When pH = pKa , the ionizable compound in question
(whether acid or base) will be half protonated and half deprotonated.
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BIOCHEM ACS Final Exam Practice Questions
with Figures and Correct Answers New Modified
Exam Currently Tested and Graded A+ 2026 Latest
A weak acid HA has a pKa of 6.78. Which of the following is true for a solution
of HA at pH 5.22?
A. Very high [HA] and essentially no [A-]
B. Higher [HA] and low [A-]
C. Equal [HA] and [A-]
D. Higher [A-] and low [HA]
<Correct Answer>>B Higher [HA] and low [A-]
My Note:
pH > pKa = deprotonated
pH < pKa = protonated
a. Give the one letter and 3 letter code for the basic amino acids.
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,2
b. Would you expect these amino acids to be on the interior or exterior of a
globular protein?
<Correct Answer>> Lys (K), Arg (R), His (H); exterior
Glutamic acid is one of 2 acidic amino acids.
a. What is the one letter and 3 letter code for the other one?
b. What is the charge of the side chains of these 2 amino acids?
<Correct Answer>> Asp (D); negative 1
Would you expect Leu to be in the interior or exterior of a globular protein?
<Correct Answer>> Interior
My Note: Leucine is NON-POLAR
Give the one letter and three letter code for the 3 amino acids that have side
chains that can get phosphorylated.
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,3
<Correct Answer>> Ser (S), Thr (T), Tyr (Y)
Which amino acid can react with itself to form a dimer by formation of a
disulfide bond?
<Correct Answer>> Cys (C)
At a pH above its pKa, the phenol group of tyrosine is .
A. protonated
B. deprotonated
<Correct Answer>> At a pH above its pKa, the phenol group of tyrosine is
DEPROTONATED.
My Note:
pH > pKa = deprotonated
pH < pKa = protonated
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At a pH below its pKa, the side chain-amino group of lysine is .
A. protonated
B. deprotonated
<Correct Answer>> At a pH below its pKa, the side chain-amino group of
lysine is PROTONATED.
My Note:
pH > pKa = deprotonated
pH < pKa = protonated
The correct operational relationship between pKa and pH is that:
A. both are log functions.
B. both are always <7 for acids, and >7 for bases.
C. These two concepts are not operationally related in any way since biological
fluids contains mixtures of too many acids and bases.
D. When pH = pKa , the compound in question will have a charge of +0.5.
E. When pH = pKa , the ionizable compound in question (whether acid or base)
will be half protonated and half deprotonated.
<Correct Answer>> E. When pH = pKa , the ionizable compound in question
(whether acid or base) will be half protonated and half deprotonated.
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