9 USMLE Pathology, Immunology and Biochemistry Quick Review Questions with Answers (Set 1)

These 9 quick USMLE review questions test high-yield facts that show up again and again on the exam: glycolysis, acanthosis nigricans, inflammatory pain mediators, radiation and the cell cycle, GVHD, multiple myeloma anemia, intersex conditions, 5-alpha reductase and Fabry disease. Each question includes the correct answer.

Written by Dr. Ray Makar, MD, author of the Repeated USMLE Questions eBook series.

Prefer video? Watch daily USMLE case questions on MedFocus by Dr. Ray on YouTube.

How to use this page: read the question, pick your answer, then tap Show Answer and Explanation.

Questions

Question 1. Which one of the following enzymes catalyzes the rate limiting step in glycolysis?

A- 6-Phosphofructo-1 kinase
B- Glyceraldehyde-3-phosphate dehydrogenase
C- Phosphofructokinase-2
D- Pyruvate kinase

A- PFK-1 (6-phosphofructo-1 kinase) catalyzes the rate limiting step in glycolysis. Citrate and ATP inhibits its activity while AMP activates it and so, it limits glycolysis.
The correct answer is A

 

Question 2. Which of the following conditions is the most likely cause of the development of velvety rash in the axilla?

A- Insulin resistance
B- Serotonin hypersecretion
C- Testosterone hypersecretion
D- Thyroid hormone deficiency

A- Insulin resistance- Acanthosis nigricans occurs in cases of diabetes and is characterized by hyperkeratotic, hyperpigmented velvety plaques in the axilla, posterior neck and groin.
The correct answer is A

 

Question 3. A patient with acute appendicitis complains of abdominal pain. Which of the following chemical mediators is responsible for this pain?

A- Histamine and serotonin
B- Leukotriene and interleukin-1
C- Prostaglandin and bradykinin
D- Tumor necrosis factor and IgG

C- Prostaglandin and bradykinin
The correct answer is C

 

Question 4. Which of the following is the checkpoint in cell development that is affected by ionizing radiation?

A- G0/G1
B- G1/S
C- S/G2
D- G2/M

D- G2/M
The correct answer is D

 

Question 5. A patient presents with pruritic rash on his face, palms and soles, bloody diarrhea and abnormal liver tests two weeks after bone marrow transplantation. Which of the following is the mechanism of this condition?

A- Activation of the donor B-lymphocytes
B- Activation of the donor T-lymphocytes
C- Activation of the host T-lymphocytes
D- Development of liver failure

B- Activation of the donor T –lymphocytes
The correct answer is B

 

Question 6. Anemia occurs in cases of multiple myeloma; most likely results from which one of the following factors?

A- Defective absorption of urine
B- Infiltration of bone marrow with massive numbers of plasma cells
C- Loss of blood due to gastrointestinal bleeding
D- Low production of hemopoietin

B- Infiltration of bone marrow with massive numbers of plasma cells. Renal failure may occur later.
The correct answer is B

 

Question 7. A 12-year-old female is evaluated for an enlarged phallus at puberty. Examination reveals no breast development, a blind vaginal pouch, and no uterus. Laboratory tests show normal levels of testosterone and estrogen and very low levels of dihydrotestosterone (DHT). What is the most likely diagnosis?

A- Female pseudohermaphrodite
B- Male pseudohermaphrodite
C- True hermaphrodite
D- Turner’s syndrome

B- Male pseudohermaphrodite- This condition is due to deficiency of the enzyme responsible for conversion of testosterone into dihydrotestosterone which is essential in the fetus for development of the prostate and external genitalia. True hermaphrodite would reveal the presence of both male and female genital organs.
The correct answer is B

 

Question 8. Which of the following is the enzyme responsible for the conversion of testosterone into dihydrotestosterone (DHT)?

A- 17 alpha-hydroxylase
B- 3-beta-hydroxylase
C- 5-alpha-reductase
D- Aromatase

C- 5-alpha-reductase- Is the enzyme responsible for the conversion of testosterone into dihydrotestosterone. Other enzymes assists in synthesis of testosterone in different stages.
The correct answer is C

 

Question 9. An autopsy of an adult shows enormous cardiomyopathy, high level of cardiac deposition of glycosphingolipids and restricted cardiocytes. Which of the following lipid storage disease is most likely the correct diagnosis?

A- Fabry’s disease
B- Gaucher’s disease
C- Niemann-Pick disease
D- Tay-Sachs disease

A- Fabry’s disease- It is an X-linked disorder caused by deficiency of alpha-galactosidase A. It leads to deposition of glycosphingolipids in different organs most commonly heart, kidneys and eyes.
The correct answer is A

 

High-yield points from this set

  • Phosphofructokinase-1 is the rate-limiting enzyme of glycolysis.
  • Prostaglandins and bradykinin cause inflammatory pain.
  • GVHD after bone marrow transplant is caused by donor T cells.
  • Fabry disease (alpha-galactosidase A deficiency) is X-linked.

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