COMSAE 115 EXAM | QUESTIONS AND ANSWERS |
VERIFIED ANSWERS PLUS RATIONALES | EXAM
ALREADY GRADED A+ | LATEST EXAM
1. A 25-year-old male presents with fatigue and pallor. Labs show hemoglobin 8 g/dL,
MCV 70 fL, and low serum ferritin. Which is the most likely cause?
A) Vitamin B12 deficiency
B) Iron deficiency
C) Chronic kidney disease
D) Hemolytic anemia
Answer: B) Iron deficiency
Rationale: Microcytic anemia with low ferritin suggests iron deficiency, the most common cause
of microcytic anemia.
2. Which enzyme is deficient in classical galactosemia?
A) Galactokinase
B) Galactose-1-phosphate uridyltransferase
C) Aldolase B
D) Hexokinase
Answer: B) Galactose-1-phosphate uridyltransferase
Rationale: Classic galactosemia is due to GALT deficiency, leading to galactose-1-phosphate
accumulation.
3. A 60-year-old man presents with sudden-onset chest pain radiating to his left arm. ECG
shows ST-segment elevation in leads II, III, and aVF. Which artery is most likely
occluded?
A) Left anterior descending
B) Right coronary artery
C) Left circumflex
D) Posterior descending artery
Answer: B) Right coronary artery
Rationale: ST elevation in II, III, aVF indicates inferior myocardial infarction, usually from right
coronary artery occlusion.
4. Which of the following is the major inhibitory neurotransmitter in the CNS?
A) Glutamate
B) GABA
C) Acetylcholine
D) Dopamine
,Answer: B) GABA
Rationale: GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the
central nervous system.
5. A patient has a lesion in the ventral horn of the spinal cord. Which symptom is expected?
A) Loss of pain and temperature
B) Spastic paralysis
C) Flaccid paralysis
D) Loss of fine touch
Answer: C) Flaccid paralysis
Rationale: Ventral horn contains lower motor neurons; damage causes flaccid paralysis of the
corresponding muscles.
6. During glycolysis, which enzyme catalyzes the conversion of fructose-6-phosphate to
fructose-1,6-bisphosphate?
A) Hexokinase
B) Phosphofructokinase-1
C) Aldolase
D) Pyruvate kinase
Answer: B) Phosphofructokinase-1
Rationale: PFK-1 is the rate-limiting enzyme of glycolysis, converting F6P to F1,6BP using
ATP.
7. Which hormone is secreted by the zona glomerulosa of the adrenal cortex?
A) Cortisol
B) Aldosterone
C) Androgens
D) Epinephrine
Answer: B) Aldosterone
Rationale: Zona glomerulosa produces mineralocorticoids, mainly aldosterone, which regulates
sodium and potassium.
8. A patient with Graves’ disease is treated with methimazole. What is the mechanism of
action?
A) Blocks T4 to T3 conversion
B) Inhibits thyroid peroxidase
C) Stimulates TSH receptor
D) Decreases iodine uptake
Answer: B) Inhibits thyroid peroxidase
Rationale: Methimazole inhibits thyroid peroxidase, preventing organification of iodine and
synthesis of T3/T4.
, 9. A 30-year-old woman presents with polyuria and polydipsia. Her serum sodium is 150
mEq/L. Urine osmolality is low. What is the most likely diagnosis?
A) SIADH
B) Diabetes insipidus
C) Hyperglycemia
D) Primary polydipsia
Answer: B) Diabetes insipidus
Rationale: High serum sodium with dilute urine indicates inability to concentrate urine,
characteristic of diabetes insipidus.
10. Which of the following bacteria produces a toxin that inhibits protein synthesis by ADP-
ribosylation of EF-2?
A) Staphylococcus aureus
B) Corynebacterium diphtheriae
C) Clostridium tetani
D) Escherichia coli
Answer: B) Corynebacterium diphtheriae
Rationale: Diphtheria toxin inhibits elongation factor 2, preventing protein synthesis.
11. In a patient with hypovolemic shock, which physiologic response is expected?
A) Decreased sympathetic tone
B) Increased renin secretion
C) Decreased heart rate
D) Decreased aldosterone
Answer: B) Increased renin secretion
Rationale: Hypovolemia activates RAAS; renin secretion increases to restore blood pressure and
volume.
12. Which vitamin deficiency leads to pellagra?
A) Vitamin B1
B) Vitamin B2
C) Vitamin B3
D) Vitamin B6
Answer: C) Vitamin B3
Rationale: Niacin (B3) deficiency causes pellagra: dermatitis, diarrhea, dementia.
13. Which artery supplies the lateral aspect of the cerebral hemisphere?
A) Anterior cerebral artery
B) Middle cerebral artery
C) Posterior cerebral artery
D) Basilar artery
, Answer: B) Middle cerebral artery
Rationale: MCA supplies lateral frontal, parietal, and temporal lobes.
14. A patient presents with jaundice, dark urine, and elevated AST>ALT. What is the most
likely etiology?
A) Viral hepatitis
B) Alcoholic hepatitis
C) Hemolytic anemia
D) Biliary obstruction
Answer: B) Alcoholic hepatitis
Rationale: AST>ALT (often >2:1) suggests alcoholic liver injury.
15. A 2-year-old boy presents with developmental delay and musty body odor. Which
enzyme deficiency is most likely?
A) Phenylalanine hydroxylase
B) Tyrosinase
C) Homogentisate oxidase
D) Branched-chain α-keto acid dehydrogenase
Answer: A) Phenylalanine hydroxylase
Rationale: PKU is due to PAH deficiency, causing accumulation of phenylalanine and musty
odor.
16. Which cranial nerve mediates the corneal reflex?
A) CN II
B) CN V and VII
C) CN III and IV
D) CN IX
Answer: B) CN V and VII
Rationale: Afferent limb: CN V (ophthalmic branch); efferent limb: CN VII (orbicularis oculi
contraction).
17. Which structure forms the blood–brain barrier?
A) Astrocyte end-feet and endothelial tight junctions
B) Microglia
C) Ependymal cells
D) Schwann cells
Answer: A) Astrocyte end-feet and endothelial tight junctions
Rationale: BBB is formed by endothelial tight junctions and astrocytic foot processes.
18. A patient with chronic renal failure develops anemia. Which deficiency is most likely?
A) Iron
B) Vitamin B12
VERIFIED ANSWERS PLUS RATIONALES | EXAM
ALREADY GRADED A+ | LATEST EXAM
1. A 25-year-old male presents with fatigue and pallor. Labs show hemoglobin 8 g/dL,
MCV 70 fL, and low serum ferritin. Which is the most likely cause?
A) Vitamin B12 deficiency
B) Iron deficiency
C) Chronic kidney disease
D) Hemolytic anemia
Answer: B) Iron deficiency
Rationale: Microcytic anemia with low ferritin suggests iron deficiency, the most common cause
of microcytic anemia.
2. Which enzyme is deficient in classical galactosemia?
A) Galactokinase
B) Galactose-1-phosphate uridyltransferase
C) Aldolase B
D) Hexokinase
Answer: B) Galactose-1-phosphate uridyltransferase
Rationale: Classic galactosemia is due to GALT deficiency, leading to galactose-1-phosphate
accumulation.
3. A 60-year-old man presents with sudden-onset chest pain radiating to his left arm. ECG
shows ST-segment elevation in leads II, III, and aVF. Which artery is most likely
occluded?
A) Left anterior descending
B) Right coronary artery
C) Left circumflex
D) Posterior descending artery
Answer: B) Right coronary artery
Rationale: ST elevation in II, III, aVF indicates inferior myocardial infarction, usually from right
coronary artery occlusion.
4. Which of the following is the major inhibitory neurotransmitter in the CNS?
A) Glutamate
B) GABA
C) Acetylcholine
D) Dopamine
,Answer: B) GABA
Rationale: GABA (gamma-aminobutyric acid) is the main inhibitory neurotransmitter in the
central nervous system.
5. A patient has a lesion in the ventral horn of the spinal cord. Which symptom is expected?
A) Loss of pain and temperature
B) Spastic paralysis
C) Flaccid paralysis
D) Loss of fine touch
Answer: C) Flaccid paralysis
Rationale: Ventral horn contains lower motor neurons; damage causes flaccid paralysis of the
corresponding muscles.
6. During glycolysis, which enzyme catalyzes the conversion of fructose-6-phosphate to
fructose-1,6-bisphosphate?
A) Hexokinase
B) Phosphofructokinase-1
C) Aldolase
D) Pyruvate kinase
Answer: B) Phosphofructokinase-1
Rationale: PFK-1 is the rate-limiting enzyme of glycolysis, converting F6P to F1,6BP using
ATP.
7. Which hormone is secreted by the zona glomerulosa of the adrenal cortex?
A) Cortisol
B) Aldosterone
C) Androgens
D) Epinephrine
Answer: B) Aldosterone
Rationale: Zona glomerulosa produces mineralocorticoids, mainly aldosterone, which regulates
sodium and potassium.
8. A patient with Graves’ disease is treated with methimazole. What is the mechanism of
action?
A) Blocks T4 to T3 conversion
B) Inhibits thyroid peroxidase
C) Stimulates TSH receptor
D) Decreases iodine uptake
Answer: B) Inhibits thyroid peroxidase
Rationale: Methimazole inhibits thyroid peroxidase, preventing organification of iodine and
synthesis of T3/T4.
, 9. A 30-year-old woman presents with polyuria and polydipsia. Her serum sodium is 150
mEq/L. Urine osmolality is low. What is the most likely diagnosis?
A) SIADH
B) Diabetes insipidus
C) Hyperglycemia
D) Primary polydipsia
Answer: B) Diabetes insipidus
Rationale: High serum sodium with dilute urine indicates inability to concentrate urine,
characteristic of diabetes insipidus.
10. Which of the following bacteria produces a toxin that inhibits protein synthesis by ADP-
ribosylation of EF-2?
A) Staphylococcus aureus
B) Corynebacterium diphtheriae
C) Clostridium tetani
D) Escherichia coli
Answer: B) Corynebacterium diphtheriae
Rationale: Diphtheria toxin inhibits elongation factor 2, preventing protein synthesis.
11. In a patient with hypovolemic shock, which physiologic response is expected?
A) Decreased sympathetic tone
B) Increased renin secretion
C) Decreased heart rate
D) Decreased aldosterone
Answer: B) Increased renin secretion
Rationale: Hypovolemia activates RAAS; renin secretion increases to restore blood pressure and
volume.
12. Which vitamin deficiency leads to pellagra?
A) Vitamin B1
B) Vitamin B2
C) Vitamin B3
D) Vitamin B6
Answer: C) Vitamin B3
Rationale: Niacin (B3) deficiency causes pellagra: dermatitis, diarrhea, dementia.
13. Which artery supplies the lateral aspect of the cerebral hemisphere?
A) Anterior cerebral artery
B) Middle cerebral artery
C) Posterior cerebral artery
D) Basilar artery
, Answer: B) Middle cerebral artery
Rationale: MCA supplies lateral frontal, parietal, and temporal lobes.
14. A patient presents with jaundice, dark urine, and elevated AST>ALT. What is the most
likely etiology?
A) Viral hepatitis
B) Alcoholic hepatitis
C) Hemolytic anemia
D) Biliary obstruction
Answer: B) Alcoholic hepatitis
Rationale: AST>ALT (often >2:1) suggests alcoholic liver injury.
15. A 2-year-old boy presents with developmental delay and musty body odor. Which
enzyme deficiency is most likely?
A) Phenylalanine hydroxylase
B) Tyrosinase
C) Homogentisate oxidase
D) Branched-chain α-keto acid dehydrogenase
Answer: A) Phenylalanine hydroxylase
Rationale: PKU is due to PAH deficiency, causing accumulation of phenylalanine and musty
odor.
16. Which cranial nerve mediates the corneal reflex?
A) CN II
B) CN V and VII
C) CN III and IV
D) CN IX
Answer: B) CN V and VII
Rationale: Afferent limb: CN V (ophthalmic branch); efferent limb: CN VII (orbicularis oculi
contraction).
17. Which structure forms the blood–brain barrier?
A) Astrocyte end-feet and endothelial tight junctions
B) Microglia
C) Ependymal cells
D) Schwann cells
Answer: A) Astrocyte end-feet and endothelial tight junctions
Rationale: BBB is formed by endothelial tight junctions and astrocytic foot processes.
18. A patient with chronic renal failure develops anemia. Which deficiency is most likely?
A) Iron
B) Vitamin B12
