COMSAE Phase 1 Form 115 Practice Exam
2026| 250 Most Tested Questions
Collection & Verified Detailed Answers |
Tutor Verified Success Exam) Graded A+
1. A patient with severe diarrhea develops a normal-anion-gap
metabolic acidosis. Which mechanism best explains this finding?
A. Increased lactate production
B. Increased ketoacid production
C. Loss of bicarbonate from the gastrointestinal tract
D. Decreased hydrogen ion secretion by the kidney
Rationale: Diarrhea causes gastrointestinal bicarbonate loss,
producing a hyperchloremic, normal-anion-gap metabolic acidosis.
2. Which enzyme is directly inhibited by fluoride in a blood sample
collected for glucose measurement?
A. Hexokinase
B. Glucose-6-phosphatase
C. Enolase
D. Pyruvate carboxylase
Rationale: Fluoride inhibits enolase and therefore slows glycolysis,
helping prevent continued glucose consumption in the specimen.
3. A deficiency of vitamin B1 most directly impairs which enzyme?
A. Glucose-6-phosphatase
B. Pyruvate dehydrogenase
C. Fructose-1,6-bisphosphatase
D. Lactate dehydrogenase
,Rationale: Thiamine pyrophosphate is a required cofactor for
pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and
transketolase.
4. Which immunoglobulin is most abundant in the serum of a healthy
adult?
A. IgA
B. IgE
C. IgM
D. IgG
Rationale: IgG is the predominant serum immunoglobulin and is the
major antibody involved in secondary immune responses.
5. A mutation changes a codon from UAU to UAA. What type of
mutation has occurred?
A. Missense
B. Silent
C. Frameshift
D. Nonsense
Rationale: UAA is a stop codon, so the mutation prematurely
terminates translation.
6. Which cellular organelle is primarily responsible for oxidative
phosphorylation?
A. Lysosome
B. Golgi apparatus
C. Mitochondrion
D. Rough endoplasmic reticulum
Rationale: The mitochondrial inner membrane contains the electron
transport chain and ATP synthase.
7. A patient has impaired conversion of phenylalanine to tyrosine.
Which enzyme is most likely deficient?
,A. Homogentisate oxidase
B. Phenylalanine hydroxylase
C. Tyrosinase
D. Branched-chain α-ketoacid dehydrogenase
Rationale: Phenylalanine hydroxylase converts phenylalanine to
tyrosine using tetrahydrobiopterin.
8. Which lipoprotein transports dietary triglycerides from the
intestine to peripheral tissues?
A. HDL
B. LDL
C. VLDL
D. Chylomicrons
Rationale: Chylomicrons carry dietary lipids from intestinal
enterocytes through the lymphatics and into circulation.
9. Which enzyme is most specific for hepatocellular injury?
A. Alkaline phosphatase
B. Creatine kinase
C. ALT
D. Amylase
Rationale: Alanine aminotransferase is relatively specific for
hepatocellular injury compared with AST.
10. A patient has prolonged bleeding, normal platelet count, and
prolonged PT. Which deficiency is most likely?
A. Factor VIII
B. Factor IX
C. Factor VII
D. Factor XII
Rationale: Factor VII is part of the extrinsic pathway and is assessed
by PT.
, 11. Which amino acid is exclusively ketogenic?
A. Alanine
B. Glutamate
C. Leucine
D. Serine
Rationale: Leucine and lysine are the only exclusively ketogenic amino
acids.
12. Which metabolic pathway occurs primarily in the cytosol?
A. Citric acid cycle
B. β-oxidation
C. Electron transport chain
D. Glycolysis
Rationale: Glycolysis occurs in the cytosol, whereas the citric acid
cycle and β-oxidation primarily occur within mitochondria.
13. A child develops hemolytic anemia after exposure to an oxidant
medication. Which enzyme deficiency is most likely?
A. Pyruvate kinase
B. Glucose-6-phosphate dehydrogenase
C. Hexokinase
D. Lactate dehydrogenase
Rationale: G6PD generates NADPH, which maintains glutathione in
its reduced form and protects erythrocytes from oxidative damage.
14. Which vitamin is required for γ-carboxylation of coagulation
factors II, VII, IX, and X?
A. Vitamin A
B. Vitamin B12
C. Vitamin C
D. Vitamin K
2026| 250 Most Tested Questions
Collection & Verified Detailed Answers |
Tutor Verified Success Exam) Graded A+
1. A patient with severe diarrhea develops a normal-anion-gap
metabolic acidosis. Which mechanism best explains this finding?
A. Increased lactate production
B. Increased ketoacid production
C. Loss of bicarbonate from the gastrointestinal tract
D. Decreased hydrogen ion secretion by the kidney
Rationale: Diarrhea causes gastrointestinal bicarbonate loss,
producing a hyperchloremic, normal-anion-gap metabolic acidosis.
2. Which enzyme is directly inhibited by fluoride in a blood sample
collected for glucose measurement?
A. Hexokinase
B. Glucose-6-phosphatase
C. Enolase
D. Pyruvate carboxylase
Rationale: Fluoride inhibits enolase and therefore slows glycolysis,
helping prevent continued glucose consumption in the specimen.
3. A deficiency of vitamin B1 most directly impairs which enzyme?
A. Glucose-6-phosphatase
B. Pyruvate dehydrogenase
C. Fructose-1,6-bisphosphatase
D. Lactate dehydrogenase
,Rationale: Thiamine pyrophosphate is a required cofactor for
pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and
transketolase.
4. Which immunoglobulin is most abundant in the serum of a healthy
adult?
A. IgA
B. IgE
C. IgM
D. IgG
Rationale: IgG is the predominant serum immunoglobulin and is the
major antibody involved in secondary immune responses.
5. A mutation changes a codon from UAU to UAA. What type of
mutation has occurred?
A. Missense
B. Silent
C. Frameshift
D. Nonsense
Rationale: UAA is a stop codon, so the mutation prematurely
terminates translation.
6. Which cellular organelle is primarily responsible for oxidative
phosphorylation?
A. Lysosome
B. Golgi apparatus
C. Mitochondrion
D. Rough endoplasmic reticulum
Rationale: The mitochondrial inner membrane contains the electron
transport chain and ATP synthase.
7. A patient has impaired conversion of phenylalanine to tyrosine.
Which enzyme is most likely deficient?
,A. Homogentisate oxidase
B. Phenylalanine hydroxylase
C. Tyrosinase
D. Branched-chain α-ketoacid dehydrogenase
Rationale: Phenylalanine hydroxylase converts phenylalanine to
tyrosine using tetrahydrobiopterin.
8. Which lipoprotein transports dietary triglycerides from the
intestine to peripheral tissues?
A. HDL
B. LDL
C. VLDL
D. Chylomicrons
Rationale: Chylomicrons carry dietary lipids from intestinal
enterocytes through the lymphatics and into circulation.
9. Which enzyme is most specific for hepatocellular injury?
A. Alkaline phosphatase
B. Creatine kinase
C. ALT
D. Amylase
Rationale: Alanine aminotransferase is relatively specific for
hepatocellular injury compared with AST.
10. A patient has prolonged bleeding, normal platelet count, and
prolonged PT. Which deficiency is most likely?
A. Factor VIII
B. Factor IX
C. Factor VII
D. Factor XII
Rationale: Factor VII is part of the extrinsic pathway and is assessed
by PT.
, 11. Which amino acid is exclusively ketogenic?
A. Alanine
B. Glutamate
C. Leucine
D. Serine
Rationale: Leucine and lysine are the only exclusively ketogenic amino
acids.
12. Which metabolic pathway occurs primarily in the cytosol?
A. Citric acid cycle
B. β-oxidation
C. Electron transport chain
D. Glycolysis
Rationale: Glycolysis occurs in the cytosol, whereas the citric acid
cycle and β-oxidation primarily occur within mitochondria.
13. A child develops hemolytic anemia after exposure to an oxidant
medication. Which enzyme deficiency is most likely?
A. Pyruvate kinase
B. Glucose-6-phosphate dehydrogenase
C. Hexokinase
D. Lactate dehydrogenase
Rationale: G6PD generates NADPH, which maintains glutathione in
its reduced form and protects erythrocytes from oxidative damage.
14. Which vitamin is required for γ-carboxylation of coagulation
factors II, VII, IX, and X?
A. Vitamin A
B. Vitamin B12
C. Vitamin C
D. Vitamin K
