BIOCHEM 210 COMPREHENSIVE BIOCHEMISTRY FINAL
EXAM ACTUAL 2026/2027 | Modules 1-8 Complete Coverage |
Portage Learning | Questions & Verified Answers | Pass
Guaranteed - A+ Graded
[Section 1: Water, pH, Buffers & Amino Acids (Q1-12)]
Q1. Which property of water is primarily responsible for its relatively high boiling point
compared to other molecules of similar molecular weight?
A. Covalent bonding between hydrogen and oxygen atoms.
B. Hydrogen bonding between water molecules. [CORRECT]
C. Ionic bonding in aqueous solutions.
D. Van der Waals interactions between water molecules.
Rationale: Extensive hydrogen bonding between water molecules creates a network
requiring significant energy to disrupt, explaining the high boiling point, surface tension,
and specific heat capacity; covalent bonds within the molecule are not responsible for
intermolecular properties.
Correct Answer: B
Q2. The pH of a solution is defined as:
A. The concentration of hydroxide ions in moles per liter.
B. The negative logarithm of the hydrogen ion concentration. [CORRECT]
C. The sum of hydrogen and hydroxide ion concentrations.
D. The ratio of acid to base concentration.
Rationale: pH = -log[H⁺], a logarithmic scale where each unit change represents a
10-fold change in hydrogen ion concentration; pOH measures hydroxide concentration.
,Correct Answer: B
Q3. A buffer solution contains 0.1 M acetic acid (pKa = 4.76) and 0.1 M sodium acetate.
What is the pH of this buffer?
A. 3.76
B. 4.76 [CORRECT]
C. 5.76
D. 7.00
Rationale: Using the Henderson-Hasselbalch equation pH = pKa + log([A⁻]/[HA]), when
[A⁻] = [HA], the ratio is 1 and log(1) = 0, so pH = pKa = 4.76.
Correct Answer: B
Q4. In the bicarbonate buffer system (H₂CO₃/HCO₃⁻), which component acts as the
weak acid that neutralizes added base?
A. HCO₃⁻
B. H₂CO₃ [CORRECT]
C. CO₂
D. OH⁻
Rationale: H₂CO₃ (carbonic acid) donates protons to neutralize added base (OH⁻),
forming HCO₃⁻ and water; HCO₃⁻ acts as the weak base that neutralizes added acid.
Correct Answer: B
Q5. Metabolic acidosis is characterized by:
A. Blood pH above 7.45 with decreased HCO₃⁻ concentration.
B. Blood pH below 7.35 with decreased HCO₃⁻ concentration or increased H₂CO₃.
[CORRECT]
C. Blood pH of exactly 7.40 with normal buffer concentrations.
D. Increased blood pH with increased partial pressure of CO₂.
,Rationale: Acidosis reflects blood pH < 7.35; metabolic acidosis involves decreased
bicarbonate or increased acid production, while respiratory acidosis involves increased
CO₂ retention.
Correct Answer: B
Q6. Which amino acid is classified as basic due to its positively charged side chain at
physiological pH?
A. Glutamate
B. Aspartate
C. Lysine [CORRECT]
D. Serine
Rationale: Lysine contains an additional amino group in its side chain (pKa ~10.5) that
is protonated and positively charged at pH 7.4; glutamate and aspartate are acidic,
while serine is polar uncharged.
Correct Answer: C
Q7. The isoelectric point (pI) of an amino acid with no ionizable side chain is calculated
as:
A. The sum of pKa1 and pKa2.
B. The average of pKa1 and pKa2. [CORRECT]
C. The difference between pKa1 and pKa2.
D. Equal to pKa1 only.
Rationale: For amino acids with non-ionizable side chains, pI = (pKa1 + pKa2)/2,
representing the pH where the molecule has no net charge and does not migrate in an
electric field.
Correct Answer: B
, Q8. Which of the following amino acids contains a sulfur atom in its side chain?
A. Methionine [CORRECT]
B. Phenylalanine
C. Tyrosine
D. Tryptophan
Rationale: Methionine contains a thioether group (-S-CH₃); cysteine also contains sulfur
(-SH). Phenylalanine, tyrosine, and tryptophan are aromatic amino acids without sulfur.
Correct Answer: A
Q9. At physiological pH (~7.4), the amino acid histidine has a side chain pKa of
approximately 6.0. What is the predominant charge state of the imidazole ring?
A. Fully protonated and positively charged.
B. Partially protonated, allowing it to act as a buffer and participate in catalysis.
[CORRECT]
C. Fully deprotonated and neutral.
D. Negatively charged.
Rationale: When pH (7.4) is above pKa (6.0), the majority of side chains are
deprotonated, but the proximity means a significant fraction remains protonated,
enabling histidine's critical role in enzyme active sites and blood buffering.
Correct Answer: B
Q10. The chirality of amino acids found in proteins is designated as:
A. D-configuration.
B. L-configuration. [CORRECT]
C. Racemic mixture.
D. Meso-configuration.
EXAM ACTUAL 2026/2027 | Modules 1-8 Complete Coverage |
Portage Learning | Questions & Verified Answers | Pass
Guaranteed - A+ Graded
[Section 1: Water, pH, Buffers & Amino Acids (Q1-12)]
Q1. Which property of water is primarily responsible for its relatively high boiling point
compared to other molecules of similar molecular weight?
A. Covalent bonding between hydrogen and oxygen atoms.
B. Hydrogen bonding between water molecules. [CORRECT]
C. Ionic bonding in aqueous solutions.
D. Van der Waals interactions between water molecules.
Rationale: Extensive hydrogen bonding between water molecules creates a network
requiring significant energy to disrupt, explaining the high boiling point, surface tension,
and specific heat capacity; covalent bonds within the molecule are not responsible for
intermolecular properties.
Correct Answer: B
Q2. The pH of a solution is defined as:
A. The concentration of hydroxide ions in moles per liter.
B. The negative logarithm of the hydrogen ion concentration. [CORRECT]
C. The sum of hydrogen and hydroxide ion concentrations.
D. The ratio of acid to base concentration.
Rationale: pH = -log[H⁺], a logarithmic scale where each unit change represents a
10-fold change in hydrogen ion concentration; pOH measures hydroxide concentration.
,Correct Answer: B
Q3. A buffer solution contains 0.1 M acetic acid (pKa = 4.76) and 0.1 M sodium acetate.
What is the pH of this buffer?
A. 3.76
B. 4.76 [CORRECT]
C. 5.76
D. 7.00
Rationale: Using the Henderson-Hasselbalch equation pH = pKa + log([A⁻]/[HA]), when
[A⁻] = [HA], the ratio is 1 and log(1) = 0, so pH = pKa = 4.76.
Correct Answer: B
Q4. In the bicarbonate buffer system (H₂CO₃/HCO₃⁻), which component acts as the
weak acid that neutralizes added base?
A. HCO₃⁻
B. H₂CO₃ [CORRECT]
C. CO₂
D. OH⁻
Rationale: H₂CO₃ (carbonic acid) donates protons to neutralize added base (OH⁻),
forming HCO₃⁻ and water; HCO₃⁻ acts as the weak base that neutralizes added acid.
Correct Answer: B
Q5. Metabolic acidosis is characterized by:
A. Blood pH above 7.45 with decreased HCO₃⁻ concentration.
B. Blood pH below 7.35 with decreased HCO₃⁻ concentration or increased H₂CO₃.
[CORRECT]
C. Blood pH of exactly 7.40 with normal buffer concentrations.
D. Increased blood pH with increased partial pressure of CO₂.
,Rationale: Acidosis reflects blood pH < 7.35; metabolic acidosis involves decreased
bicarbonate or increased acid production, while respiratory acidosis involves increased
CO₂ retention.
Correct Answer: B
Q6. Which amino acid is classified as basic due to its positively charged side chain at
physiological pH?
A. Glutamate
B. Aspartate
C. Lysine [CORRECT]
D. Serine
Rationale: Lysine contains an additional amino group in its side chain (pKa ~10.5) that
is protonated and positively charged at pH 7.4; glutamate and aspartate are acidic,
while serine is polar uncharged.
Correct Answer: C
Q7. The isoelectric point (pI) of an amino acid with no ionizable side chain is calculated
as:
A. The sum of pKa1 and pKa2.
B. The average of pKa1 and pKa2. [CORRECT]
C. The difference between pKa1 and pKa2.
D. Equal to pKa1 only.
Rationale: For amino acids with non-ionizable side chains, pI = (pKa1 + pKa2)/2,
representing the pH where the molecule has no net charge and does not migrate in an
electric field.
Correct Answer: B
, Q8. Which of the following amino acids contains a sulfur atom in its side chain?
A. Methionine [CORRECT]
B. Phenylalanine
C. Tyrosine
D. Tryptophan
Rationale: Methionine contains a thioether group (-S-CH₃); cysteine also contains sulfur
(-SH). Phenylalanine, tyrosine, and tryptophan are aromatic amino acids without sulfur.
Correct Answer: A
Q9. At physiological pH (~7.4), the amino acid histidine has a side chain pKa of
approximately 6.0. What is the predominant charge state of the imidazole ring?
A. Fully protonated and positively charged.
B. Partially protonated, allowing it to act as a buffer and participate in catalysis.
[CORRECT]
C. Fully deprotonated and neutral.
D. Negatively charged.
Rationale: When pH (7.4) is above pKa (6.0), the majority of side chains are
deprotonated, but the proximity means a significant fraction remains protonated,
enabling histidine's critical role in enzyme active sites and blood buffering.
Correct Answer: B
Q10. The chirality of amino acids found in proteins is designated as:
A. D-configuration.
B. L-configuration. [CORRECT]
C. Racemic mixture.
D. Meso-configuration.
