CHEM 210 Biochemistry Practice Mock Test 2026 2027 with
Real Test Prep Questions with Correct Answers/ Portage Chem
210 Practice Test 2026-2027
Exam
1: Amino Acids & Protein Structure (Q1–25)
Q1. Which amino acid has a unique secondary amino group (imino acid)?
A) Glycine
B) Alanine
C) Proline
D) Valine
Answer: C
Rationale: Proline has a cyclic structure where the side chain bonds to the amino
group, forming a secondary amine (imino acid), which introduces kinks in protein
chains.
Q2. At physiological pH (~7.4), the amino group of an amino acid exists primarily
as:
A) –NH₂
B) –NH₃⁺
C) –N⁻
D) –NHOH
Answer: B
Rationale: The pKa of the α-amino group is ~9–10, so at pH 7.4 it is protonated
(−NH₃⁺).
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 can oxidize to form disulfide bonds (–S–S–),
critical for protein tertiary 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 hydrogens attached to the α-carbon, so it is not chiral
(no optical activity).
Q5. The peptide bond is best described as:
A) A C–N bond with partial double bond character
B) A fully single C–N bond
C) A C–O bond
D) An S–S bond
Answer: A
Rationale: The peptide bond has resonance (40% double bond character), making
it planar and rigid.
Q6. The primary structure of a protein refers to:
A) Alpha helices and beta sheets
B) The linear sequence of amino acids
C) Three-dimensional folding
D) Subunit arrangement
,Answer: B
Rationale: Primary structure = the covalent backbone sequence of amino acids.
Q7. Which secondary structure is stabilized by hydrogen bonds between every
fourth amino acid?
A) β-sheet
B) α-helix
C) β-turn
D) Random coil
Answer: B
Rationale: In an α-helix, each carbonyl oxygen H-bonds to the amide hydrogen
four residues away.
Q8. β-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 direction) or antiparallel
(opposite directions).
Q9. Disulfide bonds are primarily involved in stabilizing which level of protein
structure?
A) Primary
B) Secondary
C) Tertiary
D) Quaternary
Answer: C
Rationale: Disulfide bridges are covalent crosslinks within a polypeptide chain
(tertiary) or between chains (quaternary).
, Q10. Which amino acid side chain is negatively charged at pH 7?
A) Lysine
B) Arginine
C) Glutamic acid
D) Histidine
Answer: C
Rationale: Glutamic acid (Glu, E) has a carboxyl side chain (pKa ~4.2), so it is
deprotonated and negatively charged at pH 7.
Q11. Which amino acid side chain is positively charged at pH 7?
A) Aspartic acid
B) Glutamic acid
C) Lysine
D) Tyrosine
Answer: C
Rationale: Lysine has an ε-amino group (pKa ~10.5), so it is protonated and
positively charged at pH 7.
Q12. The isoelectric point (pI) of an amino acid is the pH at which it:
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
1: Amino Acids & Protein Structure (Q1–25)
Q1. Which amino acid has a unique secondary amino group (imino acid)?
A) Glycine
B) Alanine
C) Proline
D) Valine
Answer: C
Rationale: Proline has a cyclic structure where the side chain bonds to the amino
group, forming a secondary amine (imino acid), which introduces kinks in protein
chains.
Q2. At physiological pH (~7.4), the amino group of an amino acid exists primarily
as:
A) –NH₂
B) –NH₃⁺
C) –N⁻
D) –NHOH
Answer: B
Rationale: The pKa of the α-amino group is ~9–10, so at pH 7.4 it is protonated
(−NH₃⁺).
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 can oxidize to form disulfide bonds (–S–S–),
critical for protein tertiary 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 hydrogens attached to the α-carbon, so it is not chiral
(no optical activity).
Q5. The peptide bond is best described as:
A) A C–N bond with partial double bond character
B) A fully single C–N bond
C) A C–O bond
D) An S–S bond
Answer: A
Rationale: The peptide bond has resonance (40% double bond character), making
it planar and rigid.
Q6. The primary structure of a protein refers to:
A) Alpha helices and beta sheets
B) The linear sequence of amino acids
C) Three-dimensional folding
D) Subunit arrangement
,Answer: B
Rationale: Primary structure = the covalent backbone sequence of amino acids.
Q7. Which secondary structure is stabilized by hydrogen bonds between every
fourth amino acid?
A) β-sheet
B) α-helix
C) β-turn
D) Random coil
Answer: B
Rationale: In an α-helix, each carbonyl oxygen H-bonds to the amide hydrogen
four residues away.
Q8. β-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 direction) or antiparallel
(opposite directions).
Q9. Disulfide bonds are primarily involved in stabilizing which level of protein
structure?
A) Primary
B) Secondary
C) Tertiary
D) Quaternary
Answer: C
Rationale: Disulfide bridges are covalent crosslinks within a polypeptide chain
(tertiary) or between chains (quaternary).
, Q10. Which amino acid side chain is negatively charged at pH 7?
A) Lysine
B) Arginine
C) Glutamic acid
D) Histidine
Answer: C
Rationale: Glutamic acid (Glu, E) has a carboxyl side chain (pKa ~4.2), so it is
deprotonated and negatively charged at pH 7.
Q11. Which amino acid side chain is positively charged at pH 7?
A) Aspartic acid
B) Glutamic acid
C) Lysine
D) Tyrosine
Answer: C
Rationale: Lysine has an ε-amino group (pKa ~10.5), so it is protonated and
positively charged at pH 7.
Q12. The isoelectric point (pI) of an amino acid is the pH at which it:
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
