CHEM 210 Biochemistry Practice Mock Test 2026 2027 with
Real Test Prep Questions with Correct Answers/ Portage Chem
210 Practice Test 2026-2027
Exam
Section 1: Amino Acids & Protein Structure (Q1–25)
Q1. Which amino acid has a secondary amino group (imino acid) and introduces
kinks into protein chains?
A) Glycine
B) Alanine
C) Proline
D) Valine
Answer: C
Rationale: Proline has a cyclic side chain that bonds to the amino group, forming a
secondary amine (imino acid). Its rigid structure disrupts alpha helices and
introduces kinks.
Q2. At physiological pH (7.4), the alpha-carboxyl group of an amino acid exists
primarily as:
A) –COOH
B) –COO⁻
C) –CH₂OH
D) –CONH₂
Answer: B
Rationale: The pKa of the alpha-carboxyl group is ~2.2, so at pH 7.4 it is
deprotonated and negatively charged (–COO⁻).
Q3. Which amino acid contains a thiol group that can form disulfide bonds?
A) Methionine
,B) Cysteine
C) Serine
D) Threonine
Answer: B
Rationale: Cysteine’s –SH group oxidizes to form disulfide bonds (–S–S–), which
stabilize tertiary and quaternary protein structure.
Q4. Which amino acid is optically inactive?
A) L-Alanine
B) D-Alanine
C) Glycine
D) L-Proline
Answer: C
Rationale: Glycine has two hydrogen atoms attached to the α-carbon, making it
achiral (no optical activity).
Q5. The peptide bond has partial double bond character due to:
A) Hydrogen bonding
B) Resonance
C) Hydrophobic effect
D) Ionic interactions
Answer: B
Rationale: Resonance delocalizes electrons between the C=O and C–N bonds,
giving the peptide bond ~40% double bond character, making it planar and rigid.
Q6. Primary structure of a protein refers to:
A) Alpha helices and beta sheets
B) Linear sequence of amino acids
C) Three-dimensional folding
D) Subunit arrangement
,Answer: B
Rationale: Primary structure = covalent backbone sequence of amino acids linked
by peptide bonds.
Q7. Which secondary structure is stabilized by hydrogen bonds between the
carbonyl oxygen of residue n and the amide nitrogen of residue n+4?
A) β-sheet
B) α-helix
C) β-turn
D) Random coil
Answer: B
Rationale: In an α-helix, each carbonyl oxygen hydrogen bonds to the NH of the
amino acid four residues away.
Q8. Beta sheets can be:
A) Parallel only
B) Antiparallel only
C) Both parallel and antiparallel
D) Neither
Answer: C
Rationale: β-sheets can be parallel (strands run same N→C direction) or
antiparallel (opposite directions), with antiparallel being more stable.
Q9. Disulfide bonds primarily stabilize which level of protein structure?
A) Primary
B) Secondary
C) Tertiary
D) Quaternary
Answer: C
Rationale: Disulfide bridges are covalent crosslinks within a single polypeptide
chain (tertiary) or between chains (quaternary).
, Q10. Which amino acid has a positively charged side chain at pH 7?
A) Glutamic acid
B) Aspartic acid
C) Lysine
D) Tyrosine
Answer: C
Rationale: Lysine has an ε-amino group (pKa ~10.5), protonated and positively
charged at pH 7.
Q11. Which amino acid has a negatively charged side chain at pH 7?
A) Lysine
B) Arginine
C) Glutamic acid
D) Histidine
Answer: C
Rationale: Glutamic acid has a carboxyl side chain (pKa ~4.2), deprotonated and
negatively charged at pH 7.
Q12. The isoelectric point (pI) is the pH at which a molecule:
A) Has maximum solubility
B) Has no net charge
C) Is fully protonated
D) Is fully deprotonated
Answer: B
Rationale: At pI, the number of positive charges equals negative charges; net
charge = 0.
Q13. Which technique separates proteins based on their isoelectric point?
A) SDS-PAGE
Real Test Prep Questions with Correct Answers/ Portage Chem
210 Practice Test 2026-2027
Exam
Section 1: Amino Acids & Protein Structure (Q1–25)
Q1. Which amino acid has a secondary amino group (imino acid) and introduces
kinks into protein chains?
A) Glycine
B) Alanine
C) Proline
D) Valine
Answer: C
Rationale: Proline has a cyclic side chain that bonds to the amino group, forming a
secondary amine (imino acid). Its rigid structure disrupts alpha helices and
introduces kinks.
Q2. At physiological pH (7.4), the alpha-carboxyl group of an amino acid exists
primarily as:
A) –COOH
B) –COO⁻
C) –CH₂OH
D) –CONH₂
Answer: B
Rationale: The pKa of the alpha-carboxyl group is ~2.2, so at pH 7.4 it is
deprotonated and negatively charged (–COO⁻).
Q3. Which amino acid contains a thiol group that can form disulfide bonds?
A) Methionine
,B) Cysteine
C) Serine
D) Threonine
Answer: B
Rationale: Cysteine’s –SH group oxidizes to form disulfide bonds (–S–S–), which
stabilize tertiary and quaternary protein structure.
Q4. Which amino acid is optically inactive?
A) L-Alanine
B) D-Alanine
C) Glycine
D) L-Proline
Answer: C
Rationale: Glycine has two hydrogen atoms attached to the α-carbon, making it
achiral (no optical activity).
Q5. The peptide bond has partial double bond character due to:
A) Hydrogen bonding
B) Resonance
C) Hydrophobic effect
D) Ionic interactions
Answer: B
Rationale: Resonance delocalizes electrons between the C=O and C–N bonds,
giving the peptide bond ~40% double bond character, making it planar and rigid.
Q6. Primary structure of a protein refers to:
A) Alpha helices and beta sheets
B) Linear sequence of amino acids
C) Three-dimensional folding
D) Subunit arrangement
,Answer: B
Rationale: Primary structure = covalent backbone sequence of amino acids linked
by peptide bonds.
Q7. Which secondary structure is stabilized by hydrogen bonds between the
carbonyl oxygen of residue n and the amide nitrogen of residue n+4?
A) β-sheet
B) α-helix
C) β-turn
D) Random coil
Answer: B
Rationale: In an α-helix, each carbonyl oxygen hydrogen bonds to the NH of the
amino acid four residues away.
Q8. Beta sheets can be:
A) Parallel only
B) Antiparallel only
C) Both parallel and antiparallel
D) Neither
Answer: C
Rationale: β-sheets can be parallel (strands run same N→C direction) or
antiparallel (opposite directions), with antiparallel being more stable.
Q9. Disulfide bonds primarily stabilize which level of protein structure?
A) Primary
B) Secondary
C) Tertiary
D) Quaternary
Answer: C
Rationale: Disulfide bridges are covalent crosslinks within a single polypeptide
chain (tertiary) or between chains (quaternary).
, Q10. Which amino acid has a positively charged side chain at pH 7?
A) Glutamic acid
B) Aspartic acid
C) Lysine
D) Tyrosine
Answer: C
Rationale: Lysine has an ε-amino group (pKa ~10.5), protonated and positively
charged at pH 7.
Q11. Which amino acid has a negatively charged side chain at pH 7?
A) Lysine
B) Arginine
C) Glutamic acid
D) Histidine
Answer: C
Rationale: Glutamic acid has a carboxyl side chain (pKa ~4.2), deprotonated and
negatively charged at pH 7.
Q12. The isoelectric point (pI) is the pH at which a molecule:
A) Has maximum solubility
B) Has no net charge
C) Is fully protonated
D) Is fully deprotonated
Answer: B
Rationale: At pI, the number of positive charges equals negative charges; net
charge = 0.
Q13. Which technique separates proteins based on their isoelectric point?
A) SDS-PAGE
