C785 Biochemistry - Module 2: Water, pH, and Protein Structure 2026
|WGU
1. Which property of water allows it to act as an efficient temperature buffer in
biological systems?
A. High surface tension
B. Low molecular weight
C. Low density as a solid
D. High specific heat capacity
Answer: D
Rationale: Water’s high specific heat capacity means it can absorb or release a large
amount of heat with minimal temperature change, helping maintain homeostasis.
2. In a water molecule, the oxygen atom carries a partial negative charge
because:
A. Oxygen is less electronegative than hydrogen
B. Hydrogen atoms repel the oxygen nucleus
C. Oxygen has fewer protons than hydrogen
D. Oxygen is more electronegative than hydrogen
Answer: D
Rationale: Electronegativity is the ability of an atom to attract electrons. Oxygen attracts
the shared electrons more strongly than hydrogen, creating a dipole.
,3. The ‘Hydrophobic Effect’ is primarily driven by:
A. Strong attraction between non-polar molecules
B. Increase in entropy of water molecules
C. Hydrogen bonding between lipids
D. Decrease in entropy of the protein
Answer: B
Rationale: When non-polar molecules cluster together, they minimize the surface area in
contact with water, allowing water molecules to be more disordered (increased entropy).
4. What is the pH of a solution with a hydrogen ion concentration [H+] of 1.0 x
10^-4 M?
A. 10
B. -4
C. 4
D. 14
Answer: C
Rationale: pH is calculated as -log[H+]. -log(10^-4) = 4.
5. According to the Bronsted-Lowry definition, an acid is a substance that:
A. Accepts a proton
B. Produces hydroxide ions
C. Donates a proton
D. Donates an electron pair
Answer: C
Rationale: Bronsted-Lowry acids are proton (H+) donors, while bases are proton
acceptors.
, 6. What is the primary buffer system maintaining the pH of human blood?
A. Bicarbonate buffer system
B. Protein buffer system
C. Phosphate buffer system
D. Hemoglobin buffer system
Answer: A
Rationale: The bicarbonate buffer system (CO2/HCO3-) is the most important
extracellular buffer for maintaining physiological pH around 7.4.
7. A buffer is most effective at resisting pH changes when:
A. The pH is much higher than the pKa
B. The pH is much lower than the pKa
C. The pH is equal to the pKa
D. The concentration of acid is zero
Answer: C
Rationale: Buffering capacity is maximal when pH = pKa, because the concentrations of the
weak acid and its conjugate base are equal.
8. If a patient is hyperventilating, what happens to their blood pH?
A. pH decreases (Respiratory Acidosis)
B. pH remains stable
C. pH increases (Respiratory Alkalosis)
D. pH decreases (Metabolic Acidosis)
Answer: C
Rationale: Hyperventilation removes CO2 from the blood. Since CO2 forms carbonic acid,
losing it causes the pH to rise, leading to respiratory alkalosis.
|WGU
1. Which property of water allows it to act as an efficient temperature buffer in
biological systems?
A. High surface tension
B. Low molecular weight
C. Low density as a solid
D. High specific heat capacity
Answer: D
Rationale: Water’s high specific heat capacity means it can absorb or release a large
amount of heat with minimal temperature change, helping maintain homeostasis.
2. In a water molecule, the oxygen atom carries a partial negative charge
because:
A. Oxygen is less electronegative than hydrogen
B. Hydrogen atoms repel the oxygen nucleus
C. Oxygen has fewer protons than hydrogen
D. Oxygen is more electronegative than hydrogen
Answer: D
Rationale: Electronegativity is the ability of an atom to attract electrons. Oxygen attracts
the shared electrons more strongly than hydrogen, creating a dipole.
,3. The ‘Hydrophobic Effect’ is primarily driven by:
A. Strong attraction between non-polar molecules
B. Increase in entropy of water molecules
C. Hydrogen bonding between lipids
D. Decrease in entropy of the protein
Answer: B
Rationale: When non-polar molecules cluster together, they minimize the surface area in
contact with water, allowing water molecules to be more disordered (increased entropy).
4. What is the pH of a solution with a hydrogen ion concentration [H+] of 1.0 x
10^-4 M?
A. 10
B. -4
C. 4
D. 14
Answer: C
Rationale: pH is calculated as -log[H+]. -log(10^-4) = 4.
5. According to the Bronsted-Lowry definition, an acid is a substance that:
A. Accepts a proton
B. Produces hydroxide ions
C. Donates a proton
D. Donates an electron pair
Answer: C
Rationale: Bronsted-Lowry acids are proton (H+) donors, while bases are proton
acceptors.
, 6. What is the primary buffer system maintaining the pH of human blood?
A. Bicarbonate buffer system
B. Protein buffer system
C. Phosphate buffer system
D. Hemoglobin buffer system
Answer: A
Rationale: The bicarbonate buffer system (CO2/HCO3-) is the most important
extracellular buffer for maintaining physiological pH around 7.4.
7. A buffer is most effective at resisting pH changes when:
A. The pH is much higher than the pKa
B. The pH is much lower than the pKa
C. The pH is equal to the pKa
D. The concentration of acid is zero
Answer: C
Rationale: Buffering capacity is maximal when pH = pKa, because the concentrations of the
weak acid and its conjugate base are equal.
8. If a patient is hyperventilating, what happens to their blood pH?
A. pH decreases (Respiratory Acidosis)
B. pH remains stable
C. pH increases (Respiratory Alkalosis)
D. pH decreases (Metabolic Acidosis)
Answer: C
Rationale: Hyperventilation removes CO2 from the blood. Since CO2 forms carbonic acid,
losing it causes the pH to rise, leading to respiratory alkalosis.
