USMLE STEP 1 LICENSE EXAM/ ACTUAL EXAM
QUESTIONS AND 100% VERIFIED ANSWERS
WITH RATIONALES GRADED A+ LATEST
Question 1
A 55-year-old man presents with progressive dyspnea and a chronic cough. He has
a 30-pack-year smoking history. Pulmonary function tests show FEV1/FVC of
0.62 and decreased FEV1. Which of the following best explains the primary
mechanism of his disease?
A. Autoimmune destruction of alveolar basement membrane
B. Loss of elastic recoil due to protease–antiprotease imbalance
C. Fibrotic thickening of alveolar septa
D. Smooth muscle hyperplasia of bronchioles
Answer: B
Rationale:
This presentation is consistent with COPD (emphysema). Smoking increases
neutrophil elastase activity and decreases alpha-1 antitrypsin function, leading to
destruction of elastin in alveolar walls and loss of elastic recoil.
Question 2
A 23-year-old woman presents with fatigue and pallor. Lab results show:
Hb 8.2 g/dL, MCV 68 fL, ferritin low, TIBC elevated. Which step in heme
synthesis is most directly affected?
A. Succinyl-CoA + glycine → ALA
B. Ferrochelatase insertion of iron into protoporphyrin IX
C. Conversion of ALA to porphobilinogen
D. Formation of coproporphyrinogen III
Answer: B
,Rationale:
Iron deficiency anemia limits the final step of heme synthesis—iron insertion into
protoporphyrin IX via ferrochelatase.
Question 3
A patient is prescribed a drug that increases cAMP in cardiac myocytes. Which
receptor is most likely activated?
A. Alpha-1 receptor
B. Beta-1 receptor
C. M2 receptor
D. D2 receptor
Answer: B
Rationale:
Beta-1 adrenergic receptors are Gs-coupled, activating adenylate cyclase →
increased cAMP → increased cardiac contractility and heart rate.
Question 4
A 40-year-old man has recurrent infections with catalase-positive organisms
including Staphylococcus aureus and Serratia marcescens. Which defect is most
likely present?
A. Myeloperoxidase deficiency
B. Chronic granulomatous disease
C. Leukocyte adhesion deficiency
D. Chediak-Higashi syndrome
Answer: B
Rationale:
Chronic granulomatous disease is due to NADPH oxidase deficiency, impairing
respiratory burst and leading to infections with catalase-positive organisms.
,Question 5
A researcher blocks RNA polymerase II in a human cell line. Which process is
most directly inhibited?
A. tRNA synthesis
B. mRNA synthesis
C. rRNA synthesis (28S, 18S, 5.8S)
D. DNA replication
Answer: B
Rationale:
RNA polymerase II transcribes mRNA in eukaryotic cells.
Question 6
A 60-year-old man with cirrhosis presents with confusion and asterixis. Which
neurotransmitter change contributes most to his condition?
A. Increased glutamate activity
B. Decreased GABA activity
C. Increased ammonia leading to astrocyte glutamine accumulation
D. Increased dopamine in the cortex
Answer: C
Rationale:
Hepatic encephalopathy is caused by ammonia accumulation, leading to astrocyte
swelling from glutamine production.
, Question 7
A child presents with recurrent viral infections and absent thymic shadow on
imaging. Which immune cell type is most affected?
A. B cells
B. Neutrophils
C. T cells
D. NK cells
Answer: C
Rationale:
DiGeorge syndrome (22q11 deletion) causes thymic hypoplasia → decreased T-
cell maturation.
Question 8
A 30-year-old woman develops hematuria after a recent upper respiratory
infection. Renal biopsy shows IgA deposition in the mesangium. Which condition
is most associated?
A. Post-streptococcal glomerulonephritis
B. IgA nephropathy
C. Goodpasture syndrome
D. Minimal change disease
Answer: B
Rationale:
IgA nephropathy presents with hematuria following mucosal infections and
mesangial IgA deposition.
QUESTIONS AND 100% VERIFIED ANSWERS
WITH RATIONALES GRADED A+ LATEST
Question 1
A 55-year-old man presents with progressive dyspnea and a chronic cough. He has
a 30-pack-year smoking history. Pulmonary function tests show FEV1/FVC of
0.62 and decreased FEV1. Which of the following best explains the primary
mechanism of his disease?
A. Autoimmune destruction of alveolar basement membrane
B. Loss of elastic recoil due to protease–antiprotease imbalance
C. Fibrotic thickening of alveolar septa
D. Smooth muscle hyperplasia of bronchioles
Answer: B
Rationale:
This presentation is consistent with COPD (emphysema). Smoking increases
neutrophil elastase activity and decreases alpha-1 antitrypsin function, leading to
destruction of elastin in alveolar walls and loss of elastic recoil.
Question 2
A 23-year-old woman presents with fatigue and pallor. Lab results show:
Hb 8.2 g/dL, MCV 68 fL, ferritin low, TIBC elevated. Which step in heme
synthesis is most directly affected?
A. Succinyl-CoA + glycine → ALA
B. Ferrochelatase insertion of iron into protoporphyrin IX
C. Conversion of ALA to porphobilinogen
D. Formation of coproporphyrinogen III
Answer: B
,Rationale:
Iron deficiency anemia limits the final step of heme synthesis—iron insertion into
protoporphyrin IX via ferrochelatase.
Question 3
A patient is prescribed a drug that increases cAMP in cardiac myocytes. Which
receptor is most likely activated?
A. Alpha-1 receptor
B. Beta-1 receptor
C. M2 receptor
D. D2 receptor
Answer: B
Rationale:
Beta-1 adrenergic receptors are Gs-coupled, activating adenylate cyclase →
increased cAMP → increased cardiac contractility and heart rate.
Question 4
A 40-year-old man has recurrent infections with catalase-positive organisms
including Staphylococcus aureus and Serratia marcescens. Which defect is most
likely present?
A. Myeloperoxidase deficiency
B. Chronic granulomatous disease
C. Leukocyte adhesion deficiency
D. Chediak-Higashi syndrome
Answer: B
Rationale:
Chronic granulomatous disease is due to NADPH oxidase deficiency, impairing
respiratory burst and leading to infections with catalase-positive organisms.
,Question 5
A researcher blocks RNA polymerase II in a human cell line. Which process is
most directly inhibited?
A. tRNA synthesis
B. mRNA synthesis
C. rRNA synthesis (28S, 18S, 5.8S)
D. DNA replication
Answer: B
Rationale:
RNA polymerase II transcribes mRNA in eukaryotic cells.
Question 6
A 60-year-old man with cirrhosis presents with confusion and asterixis. Which
neurotransmitter change contributes most to his condition?
A. Increased glutamate activity
B. Decreased GABA activity
C. Increased ammonia leading to astrocyte glutamine accumulation
D. Increased dopamine in the cortex
Answer: C
Rationale:
Hepatic encephalopathy is caused by ammonia accumulation, leading to astrocyte
swelling from glutamine production.
, Question 7
A child presents with recurrent viral infections and absent thymic shadow on
imaging. Which immune cell type is most affected?
A. B cells
B. Neutrophils
C. T cells
D. NK cells
Answer: C
Rationale:
DiGeorge syndrome (22q11 deletion) causes thymic hypoplasia → decreased T-
cell maturation.
Question 8
A 30-year-old woman develops hematuria after a recent upper respiratory
infection. Renal biopsy shows IgA deposition in the mesangium. Which condition
is most associated?
A. Post-streptococcal glomerulonephritis
B. IgA nephropathy
C. Goodpasture syndrome
D. Minimal change disease
Answer: B
Rationale:
IgA nephropathy presents with hematuria following mucosal infections and
mesangial IgA deposition.
