CHEM 219 MODULE 2: WATER, AMINO
ACIDS, AND PROTEINS QUESTIONS
WITH CORRECT ANSWERS 2026/2027
UPDATE. JUST RELEASED
1. Which property of water allows it to dissolve polar and ionic substances effectively?
A. High heat capacity
B. High dielectric constant
C. Low viscosity
D. Surface tension
Answer: B
Conceptual Explanation: Water has a high dielectric constant, which reduces the force of
attraction between oppositely charged ions, allowing them to dissolve.
2. In the Henderson-Hasselbalch equation, what happens when the concentration of the
conjugate base equals the concentration of the weak acid?
A. pH = 7.0
B. pH = pKa
C. pH = 0
D. pKa = 0
,Answer: B
Conceptual Explanation: When [A-] = [HA], the log([A-]/[HA]) term becomes log(1),
which is zero, making pH = pKa.
3. Which amino acid is considered achiral?
A. Alanine
B. Proline
C. Glycine
D. Leucine
Answer: C
Conceptual Explanation: Glycine is the only amino acid where the R-group is a hydrogen
atom, meaning the alpha-carbon is not attached to four different groups.
4. What is the characteristic geometry of the peptide bond due to resonance?
A. Tetrahedral
B. Linear
C. Planar
D. Bent
Answer: C
, Conceptual Explanation: The peptide bond has partial double-bond character, which
restricts rotation and keeps the atoms O, C, N, and H in a single plane.
5. Which amino acid contains a sulfur atom but cannot form disulfide bridges?
A. Cysteine
B. Methionine
C. Serine
D. Threonine
Answer: B
Conceptual Explanation: Methionine contains sulfur in a thioether linkage, unlike
Cysteine which has a thiol (-SH) group capable of oxidation to form disulfide bonds.
6. In an alpha-helix, the hydrogen bonds occur between the carbonyl oxygen of residue ‘n’
and the amide hydrogen of which residue?
A. n+4
B. n+2
C. n+3
D. n+1
Answer: A
Conceptual Explanation: The alpha-helix is stabilized by hydrogen bonds between the
C=O of residue n and the N-H of residue n+4.
ACIDS, AND PROTEINS QUESTIONS
WITH CORRECT ANSWERS 2026/2027
UPDATE. JUST RELEASED
1. Which property of water allows it to dissolve polar and ionic substances effectively?
A. High heat capacity
B. High dielectric constant
C. Low viscosity
D. Surface tension
Answer: B
Conceptual Explanation: Water has a high dielectric constant, which reduces the force of
attraction between oppositely charged ions, allowing them to dissolve.
2. In the Henderson-Hasselbalch equation, what happens when the concentration of the
conjugate base equals the concentration of the weak acid?
A. pH = 7.0
B. pH = pKa
C. pH = 0
D. pKa = 0
,Answer: B
Conceptual Explanation: When [A-] = [HA], the log([A-]/[HA]) term becomes log(1),
which is zero, making pH = pKa.
3. Which amino acid is considered achiral?
A. Alanine
B. Proline
C. Glycine
D. Leucine
Answer: C
Conceptual Explanation: Glycine is the only amino acid where the R-group is a hydrogen
atom, meaning the alpha-carbon is not attached to four different groups.
4. What is the characteristic geometry of the peptide bond due to resonance?
A. Tetrahedral
B. Linear
C. Planar
D. Bent
Answer: C
, Conceptual Explanation: The peptide bond has partial double-bond character, which
restricts rotation and keeps the atoms O, C, N, and H in a single plane.
5. Which amino acid contains a sulfur atom but cannot form disulfide bridges?
A. Cysteine
B. Methionine
C. Serine
D. Threonine
Answer: B
Conceptual Explanation: Methionine contains sulfur in a thioether linkage, unlike
Cysteine which has a thiol (-SH) group capable of oxidation to form disulfide bonds.
6. In an alpha-helix, the hydrogen bonds occur between the carbonyl oxygen of residue ‘n’
and the amide hydrogen of which residue?
A. n+4
B. n+2
C. n+3
D. n+1
Answer: A
Conceptual Explanation: The alpha-helix is stabilized by hydrogen bonds between the
C=O of residue n and the N-H of residue n+4.
