NBME Biochemistry Shelf Exam (2026) –
Complete 200-Question Practice Set
With Answers & Explanations | Latest Graded
A+ Study Guide
Question 1
Sickle cell anemia is due to which of the following mutations?
A) Deletion of phenylalanine at position 508
B) Substitution of glutamate with valine at position 6 of the β-globin chain
C) Substitution of lysine with glutamate at position 6 of the α-globin chain
D) Insertion of three nucleotides in the β-globin gene
Correct Answer: B - Substitution of glutamate with valine at position 6 of the β-globin
chain
Question 2
Which of the following amino acids functions as a major neurotransmitter in the central
nervous system?
A) Glycine
B) Glutamate
C) Alanine
D) Valine
Correct Answer: B - Glutamate
Question 3
The hemagglutinin (HA) protein of the influenza virus binds to which of the following?
A) CD4 receptors on T cells
B) Cytokine receptors
C) Sialic acid residues on host cells
D) MHC class I molecules
Correct Answer: B - Cytokine receptors
Question 4
A reducing-sugar test detects which of the following structural features?
A) Ketone groups only
B) Aldehyde or ketone groups capable of reducing copper ions
C) Ester linkages
D) Aromatic rings
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,Correct Answer: B - Tests for aldo-keto sugars (aldehyde or ketone groups capable of
reducing copper ions)
Question 5
Omeprazole exerts its therapeutic effect through which mechanism?
A) H2 receptor antagonism
B) Proton pump inhibition
C) Gastrin receptor blockade
D) Mucosal protection enhancement
Correct Answer: B - Proton pump inhibitor
Question 6
Which of the following are glycosaminoglycans (GAGs)?
A) Collagen and elastin
B) Heparin sulfate and chondroitin sulfate
C) Fibrin and fibrinogen
D) Albumin and globulin
Correct Answer: B - Heparin sulfate, chondroitin sulfate
Question 7
Glucuronidation is classified as which type of reaction?
A) Reduction
B) Hydrolysis
C) Oxidation
D) Conjugation
Correct Answer: C - Oxidation
Question 8
In Marfan's syndrome, the genetic mutation affects which level of fibrillin's protein
structure?
A) Primary structure
B) Secondary structure
C) Tertiary structure
D) Quaternary structure
Correct Answer: A - Primary structure
Question 9
A 45-year-old male presents with progressive involuntary movements, anxiety, slurred
speech, and difficulty concentrating. Which genetic abnormality is most likely?
A) Single nucleotide substitution in the huntingtin gene
B) Triple repeat expansion
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,C) Deletion of exon 7
D) Frameshift mutation
Correct Answer: B - Triple repeat expansion (Huntington's disease)
Question 10
Chediak-Higashi syndrome is characterized by which of the following laboratory
findings?
A) Decreased IgG and IgA
B) Hypergammaglobulinemia with significant neutropenia
C) Increased complement levels
D) Isolated thrombocytopenia
Correct Answer: B - Phagocyte deficiency → hypergammaglobulinemia, significant
neutropenia
Question 11
In a patient exposed to carbon monoxide, the oxygen-hemoglobin dissociation curve
shifts in which direction?
A) To the right
B) To the left
C) No shift occurs
D) Downward with no change in position
Correct Answer: B - To the left; increased affinity at low pO₂
Question 12
Pralidoxime chloride is used to treat organophosphate poisoning by which mechanism?
A) Blocking muscarinic receptors
B) Reactivating acetylcholinesterase
C) Inhibiting acetylcholine release
D) Blocking nicotinic receptors
Correct Answer: B - Reactivates acetylcholinesterase
Question 13
A chronic alcoholic presents with confusion, nystagmus, and ophthalmoplegia. This
presentation is most consistent with deficiency of which vitamin?
A) Vitamin B12
B) Thiamine (B1)
C) Riboflavin (B2)
D) Pyridoxine (B6)
Correct Answer: B - Thiamine deficiency (Wernicke encephalopathy)
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, Question 14
Lactase catalyzes the cleavage of which bond?
A) α(1→4) glycosidic bond between glucose units
B) β(1→4) glycosidic bond between galactose and glucose
C) α(1→6) glycosidic bond
D) β(1→4) bond between two glucose molecules
Correct Answer: B - β(1→4) galactosidase; cleaves galactose from glucose
Question 15
Fructose is absorbed from the intestinal lumen via which mechanism?
A) Sodium-dependent secondary active transport
B) Sodium-independent transporter
C) Active transport coupled with proton gradient
D) Facilitated diffusion using GLUT2
Correct Answer: B - Via sodium-independent transporter
Question 16
Which of the following disaccharidases are found on the intestinal brush border?
A) Amylase, lipase, and protease
B) Sucrase, lactase, maltase, and isomaltase
C) Pepsin, trypsin, and chymotrypsin
D) Nuclease and phosphatase
Correct Answer: B - Sucrase, lactase, maltase, isomaltase
Question 17
Orlistat, a weight loss medication, works by inhibiting which enzymes?
A) Hormone-sensitive lipase
B) Pancreatic and gastric lipase
C) Lipoprotein lipase
D) Cholesterol esterase
Correct Answer: B - Inhibits pancreatic and gastric lipase; leads to reduced fat digestion
Question 18
Dietary fiber primarily consists of which type of glycosidic bond?
A) α(1→4) glucose bonds
B) β(1→4) glucose bonds
C) α(1→6) glucose bonds
D) β(1→2) fructose bonds
Correct Answer: B - β(1→4) glucose bonds; the body lacks β(1→4) endoglucosidase
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Complete 200-Question Practice Set
With Answers & Explanations | Latest Graded
A+ Study Guide
Question 1
Sickle cell anemia is due to which of the following mutations?
A) Deletion of phenylalanine at position 508
B) Substitution of glutamate with valine at position 6 of the β-globin chain
C) Substitution of lysine with glutamate at position 6 of the α-globin chain
D) Insertion of three nucleotides in the β-globin gene
Correct Answer: B - Substitution of glutamate with valine at position 6 of the β-globin
chain
Question 2
Which of the following amino acids functions as a major neurotransmitter in the central
nervous system?
A) Glycine
B) Glutamate
C) Alanine
D) Valine
Correct Answer: B - Glutamate
Question 3
The hemagglutinin (HA) protein of the influenza virus binds to which of the following?
A) CD4 receptors on T cells
B) Cytokine receptors
C) Sialic acid residues on host cells
D) MHC class I molecules
Correct Answer: B - Cytokine receptors
Question 4
A reducing-sugar test detects which of the following structural features?
A) Ketone groups only
B) Aldehyde or ketone groups capable of reducing copper ions
C) Ester linkages
D) Aromatic rings
1|Page
,Correct Answer: B - Tests for aldo-keto sugars (aldehyde or ketone groups capable of
reducing copper ions)
Question 5
Omeprazole exerts its therapeutic effect through which mechanism?
A) H2 receptor antagonism
B) Proton pump inhibition
C) Gastrin receptor blockade
D) Mucosal protection enhancement
Correct Answer: B - Proton pump inhibitor
Question 6
Which of the following are glycosaminoglycans (GAGs)?
A) Collagen and elastin
B) Heparin sulfate and chondroitin sulfate
C) Fibrin and fibrinogen
D) Albumin and globulin
Correct Answer: B - Heparin sulfate, chondroitin sulfate
Question 7
Glucuronidation is classified as which type of reaction?
A) Reduction
B) Hydrolysis
C) Oxidation
D) Conjugation
Correct Answer: C - Oxidation
Question 8
In Marfan's syndrome, the genetic mutation affects which level of fibrillin's protein
structure?
A) Primary structure
B) Secondary structure
C) Tertiary structure
D) Quaternary structure
Correct Answer: A - Primary structure
Question 9
A 45-year-old male presents with progressive involuntary movements, anxiety, slurred
speech, and difficulty concentrating. Which genetic abnormality is most likely?
A) Single nucleotide substitution in the huntingtin gene
B) Triple repeat expansion
2|Page
,C) Deletion of exon 7
D) Frameshift mutation
Correct Answer: B - Triple repeat expansion (Huntington's disease)
Question 10
Chediak-Higashi syndrome is characterized by which of the following laboratory
findings?
A) Decreased IgG and IgA
B) Hypergammaglobulinemia with significant neutropenia
C) Increased complement levels
D) Isolated thrombocytopenia
Correct Answer: B - Phagocyte deficiency → hypergammaglobulinemia, significant
neutropenia
Question 11
In a patient exposed to carbon monoxide, the oxygen-hemoglobin dissociation curve
shifts in which direction?
A) To the right
B) To the left
C) No shift occurs
D) Downward with no change in position
Correct Answer: B - To the left; increased affinity at low pO₂
Question 12
Pralidoxime chloride is used to treat organophosphate poisoning by which mechanism?
A) Blocking muscarinic receptors
B) Reactivating acetylcholinesterase
C) Inhibiting acetylcholine release
D) Blocking nicotinic receptors
Correct Answer: B - Reactivates acetylcholinesterase
Question 13
A chronic alcoholic presents with confusion, nystagmus, and ophthalmoplegia. This
presentation is most consistent with deficiency of which vitamin?
A) Vitamin B12
B) Thiamine (B1)
C) Riboflavin (B2)
D) Pyridoxine (B6)
Correct Answer: B - Thiamine deficiency (Wernicke encephalopathy)
3|Page
, Question 14
Lactase catalyzes the cleavage of which bond?
A) α(1→4) glycosidic bond between glucose units
B) β(1→4) glycosidic bond between galactose and glucose
C) α(1→6) glycosidic bond
D) β(1→4) bond between two glucose molecules
Correct Answer: B - β(1→4) galactosidase; cleaves galactose from glucose
Question 15
Fructose is absorbed from the intestinal lumen via which mechanism?
A) Sodium-dependent secondary active transport
B) Sodium-independent transporter
C) Active transport coupled with proton gradient
D) Facilitated diffusion using GLUT2
Correct Answer: B - Via sodium-independent transporter
Question 16
Which of the following disaccharidases are found on the intestinal brush border?
A) Amylase, lipase, and protease
B) Sucrase, lactase, maltase, and isomaltase
C) Pepsin, trypsin, and chymotrypsin
D) Nuclease and phosphatase
Correct Answer: B - Sucrase, lactase, maltase, isomaltase
Question 17
Orlistat, a weight loss medication, works by inhibiting which enzymes?
A) Hormone-sensitive lipase
B) Pancreatic and gastric lipase
C) Lipoprotein lipase
D) Cholesterol esterase
Correct Answer: B - Inhibits pancreatic and gastric lipase; leads to reduced fat digestion
Question 18
Dietary fiber primarily consists of which type of glycosidic bond?
A) α(1→4) glucose bonds
B) β(1→4) glucose bonds
C) α(1→6) glucose bonds
D) β(1→2) fructose bonds
Correct Answer: B - β(1→4) glucose bonds; the body lacks β(1→4) endoglucosidase
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