C785 Biochemistry: Acid-Base Balance & Metabolic Pathways
Integration 2026 |WGU
1. Which buffer system is the primary extracellular buffer responsible for
maintaining the pH of human blood?
A. Phosphate buffer system
B. Bicarbonate buffer system
C. Protein buffer system
D. Hemoglobin buffer system
Answer: B
Rationale: The bicarbonate buffer system is the most important extracellular buffer in the
blood, managed by the lungs (CO2) and kidneys (HCO3-).
2. In a state of metabolic acidosis, how does the respiratory system typically
compensate?
A. By decreasing the respiratory rate to retain CO2
B. By shifting to anaerobic metabolism
C. By decreasing tidal volume
D. By increasing the respiratory rate to expel CO2
Answer: D
Rationale: Hyperventilation (increased rate) reduces the partial pressure of CO2, which
helps raise the blood pH back toward the normal range.
,3. Which enzyme serves as the primary rate-limiting step in glycolysis?
A. Phosphofructokinase-1 (PFK-1)
B. Pyruvate Kinase
C. Hexokinase
D. Aldolase
Answer: A
Rationale: PFK-1 is the key regulatory enzyme in glycolysis, inhibited by high ATP and
citrate, and activated by AMP and fructose-2,6-bisphosphate.
4. What is the primary site of gluconeogenesis in the human body?
A. Skeletal muscle
B. Liver
C. Brain
D. Adipose tissue
Answer: B
Rationale: The liver is the main organ for gluconeogenesis, ensuring blood glucose levels
are maintained during fasting; the kidneys also contribute during prolonged starvation.
5. During the TCA cycle, which molecule combines with Acetyl-CoA to form
Citrate?
A. Pyruvate
B. Malate
C. Oxaloacetate
D. Succinate
Answer: C
Rationale: Oxaloacetate (4 carbons) combines with Acetyl-CoA (2 carbons) to form Citrate
(6 carbons), catalyzed by Citrate Synthase.
, 6. Which molecule acts as the final electron acceptor in the Electron Transport
Chain (ETC)?
A. Oxygen (O2)
B. Water
C. NAD+
D. FAD
Answer: A
Rationale: Molecular oxygen is the final electron acceptor at Complex IV, where it is
reduced to form water.
7. Which hormone is primarily responsible for stimulating glycogen breakdown
in the liver during low blood glucose?
A. Insulin
B. Glucagon
C. Cortisol
D. Thyroxine
Answer: B
Rationale: Glucagon is released by the pancreas in response to low blood glucose to
stimulate glycogenolysis and gluconeogenesis in the liver.
8. What is the net ATP yield of one molecule of glucose undergoing anaerobic
glycolysis?
A. 36 ATP
B. 4 ATP
C. 32 ATP
D. 2 ATP
Answer: D
Rationale: Anaerobic glycolysis produces a net of 2 ATP per glucose molecule, as 2 are
consumed and 4 are produced.
Integration 2026 |WGU
1. Which buffer system is the primary extracellular buffer responsible for
maintaining the pH of human blood?
A. Phosphate buffer system
B. Bicarbonate buffer system
C. Protein buffer system
D. Hemoglobin buffer system
Answer: B
Rationale: The bicarbonate buffer system is the most important extracellular buffer in the
blood, managed by the lungs (CO2) and kidneys (HCO3-).
2. In a state of metabolic acidosis, how does the respiratory system typically
compensate?
A. By decreasing the respiratory rate to retain CO2
B. By shifting to anaerobic metabolism
C. By decreasing tidal volume
D. By increasing the respiratory rate to expel CO2
Answer: D
Rationale: Hyperventilation (increased rate) reduces the partial pressure of CO2, which
helps raise the blood pH back toward the normal range.
,3. Which enzyme serves as the primary rate-limiting step in glycolysis?
A. Phosphofructokinase-1 (PFK-1)
B. Pyruvate Kinase
C. Hexokinase
D. Aldolase
Answer: A
Rationale: PFK-1 is the key regulatory enzyme in glycolysis, inhibited by high ATP and
citrate, and activated by AMP and fructose-2,6-bisphosphate.
4. What is the primary site of gluconeogenesis in the human body?
A. Skeletal muscle
B. Liver
C. Brain
D. Adipose tissue
Answer: B
Rationale: The liver is the main organ for gluconeogenesis, ensuring blood glucose levels
are maintained during fasting; the kidneys also contribute during prolonged starvation.
5. During the TCA cycle, which molecule combines with Acetyl-CoA to form
Citrate?
A. Pyruvate
B. Malate
C. Oxaloacetate
D. Succinate
Answer: C
Rationale: Oxaloacetate (4 carbons) combines with Acetyl-CoA (2 carbons) to form Citrate
(6 carbons), catalyzed by Citrate Synthase.
, 6. Which molecule acts as the final electron acceptor in the Electron Transport
Chain (ETC)?
A. Oxygen (O2)
B. Water
C. NAD+
D. FAD
Answer: A
Rationale: Molecular oxygen is the final electron acceptor at Complex IV, where it is
reduced to form water.
7. Which hormone is primarily responsible for stimulating glycogen breakdown
in the liver during low blood glucose?
A. Insulin
B. Glucagon
C. Cortisol
D. Thyroxine
Answer: B
Rationale: Glucagon is released by the pancreas in response to low blood glucose to
stimulate glycogenolysis and gluconeogenesis in the liver.
8. What is the net ATP yield of one molecule of glucose undergoing anaerobic
glycolysis?
A. 36 ATP
B. 4 ATP
C. 32 ATP
D. 2 ATP
Answer: D
Rationale: Anaerobic glycolysis produces a net of 2 ATP per glucose molecule, as 2 are
consumed and 4 are produced.
