COMSAE Phase 1 Form ASA 122
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 54-year-old man with chronic alcoholism develops confusion,
ophthalmoplegia, and difficulty walking. Laboratory testing reveals
impaired glucose metabolism. Deficiency of which vitamin most
directly affects the enzyme complex responsible for oxidative
decarboxylation of pyruvate?
A. Vitamin B2
B. Vitamin B3
C. Vitamin B6
D. Vitamin B1
Answer: D. Vitamin B1
Rationale: Thiamine (vitamin B1) is a required cofactor for pyruvate
dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase.
Deficiency causes impaired carbohydrate metabolism and leads to
Wernicke encephalopathy in alcohol use disorder.
2. A patient with a mutation affecting collagen synthesis develops
hypermobile joints and fragile connective tissue. Which amino acid
modification is most likely impaired?
,A. Hydroxylation of proline and lysine
B. Addition of glucose residues to tyrosine
C. Conversion of alanine to pyruvate
D. Methylation of histidine
Answer: A. Hydroxylation of proline and lysine
Rationale: Collagen requires hydroxylation of proline and lysine
residues, a process dependent on vitamin C. Defects impair collagen
stability and wound healing.
3. A researcher studies a membrane protein that allows rapid
movement of water across cell membranes. Which structure is being
examined?
A. Sodium-potassium ATPase
B. Aquaporin channel
C. Voltage-gated calcium channel
D. Na+/glucose cotransporter
Answer: B. Aquaporin channel
Rationale: Aquaporins are membrane proteins that permit passive
water movement across cell membranes following osmotic gradients.
4. A newborn presents with severe hypotonia and inability to
generate energy during fasting. Testing reveals defective breakdown
of fatty acids. Which metabolic pathway is impaired?
A. Glycolysis
B. β-oxidation
C. Pentose phosphate pathway
D. Urea cycle
,Answer: B. β-oxidation
Rationale: Fatty acid β-oxidation produces acetyl-CoA and energy
during fasting. Defects can cause hypoketotic hypoglycemia and
muscle weakness.
5. A patient receives a medication that blocks bacterial cell wall
synthesis by binding penicillin-binding proteins. Which structure is
directly affected?
A. Peptidoglycan layer
B. Lipopolysaccharide membrane
C. Ribosomal RNA
D. DNA gyrase
Answer: A. Peptidoglycan layer
Rationale: β-lactam antibiotics inhibit transpeptidation, preventing
bacterial peptidoglycan cross-linking and causing cell wall instability.
6. A patient has destruction of peripheral myelin caused by immune-
mediated injury. Which cell type is responsible for producing myelin
in the peripheral nervous system?
A. Oligodendrocyte
B. Schwann cell
C. Astrocyte
D. Microglia
Answer: B. Schwann cell
Rationale: Schwann cells myelinate peripheral nerves, whereas
oligodendrocytes produce myelin in the CNS.
, 7. A mutation prevents separation of homologous chromosomes
during meiosis. This defect is called:
A. Translocation
B. Nondisjunction
C. Deletion
D. Inversion
Answer: B. Nondisjunction
Rationale: Nondisjunction occurs when chromosomes fail to separate
properly, producing abnormal chromosome numbers such as trisomy
21.
8. A patient develops metabolic acidosis with increased lactate
production after tissue hypoxia. Which enzyme converts pyruvate into
lactate?
A. Pyruvate carboxylase
B. Lactate dehydrogenase
C. Citrate synthase
D. Hexokinase
Answer: B. Lactate dehydrogenase
Rationale: Lactate dehydrogenase converts pyruvate to lactate,
regenerating NAD+ needed for continued glycolysis during anaerobic
metabolism.
9. A patient has weakness of facial expression muscles following
injury to a cranial nerve. Which nerve is affected?
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 54-year-old man with chronic alcoholism develops confusion,
ophthalmoplegia, and difficulty walking. Laboratory testing reveals
impaired glucose metabolism. Deficiency of which vitamin most
directly affects the enzyme complex responsible for oxidative
decarboxylation of pyruvate?
A. Vitamin B2
B. Vitamin B3
C. Vitamin B6
D. Vitamin B1
Answer: D. Vitamin B1
Rationale: Thiamine (vitamin B1) is a required cofactor for pyruvate
dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase.
Deficiency causes impaired carbohydrate metabolism and leads to
Wernicke encephalopathy in alcohol use disorder.
2. A patient with a mutation affecting collagen synthesis develops
hypermobile joints and fragile connective tissue. Which amino acid
modification is most likely impaired?
,A. Hydroxylation of proline and lysine
B. Addition of glucose residues to tyrosine
C. Conversion of alanine to pyruvate
D. Methylation of histidine
Answer: A. Hydroxylation of proline and lysine
Rationale: Collagen requires hydroxylation of proline and lysine
residues, a process dependent on vitamin C. Defects impair collagen
stability and wound healing.
3. A researcher studies a membrane protein that allows rapid
movement of water across cell membranes. Which structure is being
examined?
A. Sodium-potassium ATPase
B. Aquaporin channel
C. Voltage-gated calcium channel
D. Na+/glucose cotransporter
Answer: B. Aquaporin channel
Rationale: Aquaporins are membrane proteins that permit passive
water movement across cell membranes following osmotic gradients.
4. A newborn presents with severe hypotonia and inability to
generate energy during fasting. Testing reveals defective breakdown
of fatty acids. Which metabolic pathway is impaired?
A. Glycolysis
B. β-oxidation
C. Pentose phosphate pathway
D. Urea cycle
,Answer: B. β-oxidation
Rationale: Fatty acid β-oxidation produces acetyl-CoA and energy
during fasting. Defects can cause hypoketotic hypoglycemia and
muscle weakness.
5. A patient receives a medication that blocks bacterial cell wall
synthesis by binding penicillin-binding proteins. Which structure is
directly affected?
A. Peptidoglycan layer
B. Lipopolysaccharide membrane
C. Ribosomal RNA
D. DNA gyrase
Answer: A. Peptidoglycan layer
Rationale: β-lactam antibiotics inhibit transpeptidation, preventing
bacterial peptidoglycan cross-linking and causing cell wall instability.
6. A patient has destruction of peripheral myelin caused by immune-
mediated injury. Which cell type is responsible for producing myelin
in the peripheral nervous system?
A. Oligodendrocyte
B. Schwann cell
C. Astrocyte
D. Microglia
Answer: B. Schwann cell
Rationale: Schwann cells myelinate peripheral nerves, whereas
oligodendrocytes produce myelin in the CNS.
, 7. A mutation prevents separation of homologous chromosomes
during meiosis. This defect is called:
A. Translocation
B. Nondisjunction
C. Deletion
D. Inversion
Answer: B. Nondisjunction
Rationale: Nondisjunction occurs when chromosomes fail to separate
properly, producing abnormal chromosome numbers such as trisomy
21.
8. A patient develops metabolic acidosis with increased lactate
production after tissue hypoxia. Which enzyme converts pyruvate into
lactate?
A. Pyruvate carboxylase
B. Lactate dehydrogenase
C. Citrate synthase
D. Hexokinase
Answer: B. Lactate dehydrogenase
Rationale: Lactate dehydrogenase converts pyruvate to lactate,
regenerating NAD+ needed for continued glycolysis during anaerobic
metabolism.
9. A patient has weakness of facial expression muscles following
injury to a cranial nerve. Which nerve is affected?
