USMLE STEP 1 PRACTICE LATEST EXAM 2026
UPDATE 100 QUESTIONS AND DETAILED VERIFIED
ANSWERS FROM ACTUAL EXAMS TEST GRADE A+
1.
A 25-year-old presents with fatigue, pallor, and glossitis. Lab shows macrocytic
anemia. Which vitamin is most likely deficient?
A. Vitamin B1
B. Vitamin B9
C. Vitamin C
D. Vitamin K
Answer: B. Vitamin B9
Folate deficiency causes megaloblastic (macrocytic) anemia with glossitis and is
common in pregnancy or malnutrition.
2.
Which enzyme is deficient in Phenylketonuria (PKU)?
A. Tyrosinase
B. Phenylalanine hydroxylase
C. Homogentisate oxidase
D. Glucose-6-phosphatase
Answer: B. Phenylalanine hydroxylase
PKU results from inability to convert phenylalanine to tyrosine.
3.
,Which immune cell is primarily responsible for antibody production?
A. Neutrophils
B. B lymphocytes
C. Macrophages
D. NK cells
Answer: B. B lymphocytes
B cells differentiate into plasma cells that produce antibodies.
4.
Which organism is classically associated with “rice-water stools”?
A. Shigella
B. Vibrio cholerae
C. E. coli O157:H7
D. Salmonella typhi
Answer: B. Vibrio cholerae
Cholera toxin increases cAMP causing profuse watery diarrhea.
5.
Which vitamin deficiency causes night blindness?
A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K
Answer: A. Vitamin A
Vitamin A is required for rhodopsin in rod cells.
6.
Which structure produces cerebrospinal fluid (CSF)?
A. Choroid plexus
,B. Dura mater
C. Arachnoid granulations
D. Pia mater
Answer: A. Choroid plexus
CSF is produced in ventricles by the choroid plexus.
7.
Which antibiotic inhibits bacterial cell wall synthesis?
A. Tetracycline
B. Penicillin
C. Chloramphenicol
D. Ciprofloxacin
Answer: B. Penicillin
Beta-lactams block peptidoglycan cross-linking.
8.
Which organ is primarily responsible for drug metabolism?
A. Kidney
B. Liver
C. Lung
D. Spleen
Answer: B. Liver
Hepatic cytochrome P450 system metabolizes most drugs.
9.
Which hormone increases blood calcium levels?
A. Calcitonin
B. Parathyroid hormone
C. Insulin
, D. Aldosterone
Answer: B. Parathyroid hormone
PTH increases calcium via bone resorption and renal reabsorption.
10.
Which condition is associated with “cobblestone” mucosa?
A. Ulcerative colitis
B. Crohn disease
C. IBS
D. Celiac disease
Answer: B. Crohn disease
Transmural inflammation causes skip lesions and cobblestoning.
11.
Which virus is associated with cervical cancer?
A. HSV-1
B. HPV 16 & 18
C. EBV
D. CMV
Answer: B. HPV 16 & 18
High-risk HPV types integrate into host DNA causing malignancy.
12.
Which cell type secretes insulin?
A. Alpha cells
B. Beta cells
C. Delta cells
D. PP cells
UPDATE 100 QUESTIONS AND DETAILED VERIFIED
ANSWERS FROM ACTUAL EXAMS TEST GRADE A+
1.
A 25-year-old presents with fatigue, pallor, and glossitis. Lab shows macrocytic
anemia. Which vitamin is most likely deficient?
A. Vitamin B1
B. Vitamin B9
C. Vitamin C
D. Vitamin K
Answer: B. Vitamin B9
Folate deficiency causes megaloblastic (macrocytic) anemia with glossitis and is
common in pregnancy or malnutrition.
2.
Which enzyme is deficient in Phenylketonuria (PKU)?
A. Tyrosinase
B. Phenylalanine hydroxylase
C. Homogentisate oxidase
D. Glucose-6-phosphatase
Answer: B. Phenylalanine hydroxylase
PKU results from inability to convert phenylalanine to tyrosine.
3.
,Which immune cell is primarily responsible for antibody production?
A. Neutrophils
B. B lymphocytes
C. Macrophages
D. NK cells
Answer: B. B lymphocytes
B cells differentiate into plasma cells that produce antibodies.
4.
Which organism is classically associated with “rice-water stools”?
A. Shigella
B. Vibrio cholerae
C. E. coli O157:H7
D. Salmonella typhi
Answer: B. Vibrio cholerae
Cholera toxin increases cAMP causing profuse watery diarrhea.
5.
Which vitamin deficiency causes night blindness?
A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K
Answer: A. Vitamin A
Vitamin A is required for rhodopsin in rod cells.
6.
Which structure produces cerebrospinal fluid (CSF)?
A. Choroid plexus
,B. Dura mater
C. Arachnoid granulations
D. Pia mater
Answer: A. Choroid plexus
CSF is produced in ventricles by the choroid plexus.
7.
Which antibiotic inhibits bacterial cell wall synthesis?
A. Tetracycline
B. Penicillin
C. Chloramphenicol
D. Ciprofloxacin
Answer: B. Penicillin
Beta-lactams block peptidoglycan cross-linking.
8.
Which organ is primarily responsible for drug metabolism?
A. Kidney
B. Liver
C. Lung
D. Spleen
Answer: B. Liver
Hepatic cytochrome P450 system metabolizes most drugs.
9.
Which hormone increases blood calcium levels?
A. Calcitonin
B. Parathyroid hormone
C. Insulin
, D. Aldosterone
Answer: B. Parathyroid hormone
PTH increases calcium via bone resorption and renal reabsorption.
10.
Which condition is associated with “cobblestone” mucosa?
A. Ulcerative colitis
B. Crohn disease
C. IBS
D. Celiac disease
Answer: B. Crohn disease
Transmural inflammation causes skip lesions and cobblestoning.
11.
Which virus is associated with cervical cancer?
A. HSV-1
B. HPV 16 & 18
C. EBV
D. CMV
Answer: B. HPV 16 & 18
High-risk HPV types integrate into host DNA causing malignancy.
12.
Which cell type secretes insulin?
A. Alpha cells
B. Beta cells
C. Delta cells
D. PP cells
