10 USMLE Step 1 Mixed Review Questions with Answers (Set 7)

These 10 quick USMLE review questions test high-yield facts that show up again and again on the exam: urine chloride, alcohol metabolism, pyruvate dehydrogenase, type 2 diabetes, body heat, anthrax, hairy leukoplakia, herpes simplex and spore stains. 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 urine electrolytes is the best to estimate extracellular fluid (ECF) volume in metabolic alkalosis?

A- Urine anion gap
B- Urine chloride
C- Urine sodium
D- Urine urea

B- Urine chloride- In metabolic alkalosis, urine chloride is the best indicator of extracellular fluid (ECF) volume status. A low urine chloride (<10–20 mEq/L) suggests chloride-responsive alkalosis (often due to volume depletion), while a high urine chloride indicates chloride-resistant alkalosis.
The correct answer is B

 

Question 2. Conversion of ethanol to acetate will result in increase production of which of the following?

A- NAD
B- NADH
C- Oxaloacetate
D- Pyruvate

B- NADH- Ethanol is metabolized in two major steps (ethanol → acetaldehyde → acetate), and both steps use NAD⁺ and produce NADH. This leads to an increased NADH/NAD⁺ ratio, which contributes to lactic acidosis, hypoglycemia, and fatty liver.
The correct answer is B

 

Question 3. Alcohol is oxidized in the liver by which one of the following enzymes?

A- Alcohol decarboxylase
B- Alcohol dehydrogenase
C- Alcohol oxidase
D- Alcohol reductase

B- Alcohol dehydrogenase- It is the only real enzyme, others are distractions
The correct answer is B

 

Question 4. Deficiency of which of the following enzymes results in elevated serum levels of alanine and lactate?

A- Alanine aminotransferase
B- Glucose-6-phosphatase
C- Lactate dehydrogenase
D- Pyruvate dehydrogenase

D- Pyruvate dehydrogenase- PDH deficiency leads pyruvate to take another pathway and converted to alanine by alanine aminotransferase and to lactate by lactate dehydrogenase.
The correct answer is D

 

Question 5. Which of the following is the most common etiology of type II diabetes?

A- Altered hormone-receptor complex
B- Increased hepatic glycogen breakdown
C- Insulin receptor deficiency
D- Low insulin production

A- Altered hormone-receptor complex- Low insulin production is the etiology of type 1.
The correct answer is A

 

Question 6. Which of the following effects is caused by alcohol intake?

A- Decreased body heat loss
B- Increased body heat loss
C- Increased body temperature
D- No effect on body temperature or body heat loss

B- Increased body heat loss- Alcohol causes peripheral vasodilation, which makes warm blood move closer to the skin surface. This leads to increased heat loss, even though the person may feel warm.
The correct answer is B

 

Question 7. A middle-aged male presents with an edematous circular skin lesion of black eschar. Which of the following bacteria is the most likely causative organism of this condition?

A- Bacillus anthracis
B- Pneumonitis aeruginosa
C- Staphylococcus aureus
D- Streptococcus viridans

A- Bacillus anthracis- A painless, edematous skin lesion with a black eschar is characteristic of cutaneous anthrax, caused by Bacillus anthracis.
The correct answer is A

 

Question 8. Which of the following organisms is responsible for the development of oral hairy leukoplakia in HIV patients?

A- Bartonella henselae
B- Candida albicans
C- Epstein-Barr virus
D- Human papilloma virus

C- Epstein-Barr virus- Candida can cause oral thrush while EBV causes leukoplakia on lateral tongue.
The correct answer is C

 

Question 9. Which of the following is the most likely rout of transmission of herpes simplex virus-1?

A- Congenital transfusion
B- Food contamination
C- Respiratory secretions and saliva
D- Sexual contact and perinatal

C- Respiratory secretions and saliva- A, Cytomegalovirus. B, Hepatitis A, D, Herpes simplex virus-2
The correct answer is C

 

Question 10. Which of the following methods is the most likely to demonstrate spores?

A- Acid-fast stain
B- Gram stain
C- India ink stain
D- Malachite green stain

D- Malachite green stain- Spores are observed by staining with malachite green and then alcohol treatment prevents decolorization and they will be counterstained.
The correct answer is D

 

High-yield points from this set

  • Alcohol metabolism increases NADH.
  • Pyruvate dehydrogenase deficiency raises alanine and lactate.
  • A painless black eschar = cutaneous anthrax.
  • EBV causes oral hairy leukoplakia.

Keep practicing

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