COMSAE PHASE 1 FORM 113
COMPREHENSIVE REVIEW &
PRACTICE TEST EXAM QUESTIONS
WITH CORRECT ANSWERS PLUS
RATIONALES 2026/2027 EDITION
WITH INSTANT PDF DOWNLOAD
1. A 24-year-old man develops severe muscle cramps after
prolonged exercise in hot weather. Laboratory studies show an
elevated serum creatine kinase level. Which cellular structure is
primarily responsible for releasing calcium needed for skeletal
muscle contraction?
A. Golgi apparatus
B. Sarcoplasmic reticulum
C. Rough endoplasmic reticulum
D. Lysosome
E. Peroxisome
Correct Answer: B. Sarcoplasmic reticulum
The sarcoplasmic reticulum is a specialized form of smooth
endoplasmic reticulum that stores and releases calcium in
skeletal muscle. Depolarization triggers calcium release, allowing
calcium to bind troponin C and initiate actin-myosin interaction.
2. A newborn develops profound hypoglycemia, lactic acidosis,
and hepatomegaly after beginning feeds. Testing demonstrates
,impaired conversion of glucose-6-phosphate to free glucose.
Which enzyme is deficient?
A. Glucose-6-phosphatase
B. Pyruvate carboxylase
C. Glycogen phosphorylase
D. Hexokinase
E. Fructose-1,6-bisphosphatase
Correct Answer: A. Glucose-6-phosphatase
Glucose-6-phosphatase deficiency causes von Gierke disease, a
glycogen storage disorder characterized by severe fasting
hypoglycemia, lactic acidosis, hyperuricemia, hyperlipidemia,
and hepatomegaly. The enzyme is required for the final step of
both glycogenolysis and gluconeogenesis.
3. Which amino acid is most likely to be deficient in a patient
receiving a long-term parenteral nutrition regimen that lacks
adequate protein supplementation?
A. Tyrosine
B. Glutamine
C. Phenylalanine
D. Tryptophan
E. Methionine
Correct Answer: B. Glutamine
Glutamine is a major nitrogen donor and an important fuel source
for rapidly dividing cells, including enterocytes and immune cells.
During severe illness, it can become conditionally essential
because endogenous production may not meet metabolic
demands.
,4. A patient with chronic kidney disease develops normocytic
anemia. Which mechanism best explains this finding?
A. Increased hepcidin degradation
B. Reduced erythropoietin production
C. Increased red blood cell membrane synthesis
D. Increased intestinal iron absorption
E. Increased erythrocyte lifespan
Correct Answer: B. Reduced erythropoietin production
Renal peritubular interstitial cells normally produce
erythropoietin in response to tissue hypoxia. Chronic kidney
disease decreases erythropoietin production, resulting in
decreased erythrocyte production and a typically normocytic,
normochromic anemia.
5. A 19-year-old woman has recurrent infections with
encapsulated bacteria. Laboratory testing demonstrates absent
mature B cells. Which immunoglobulin abnormality is most
likely?
A. Increased IgE only
B. Isolated increased IgA
C. Markedly decreased immunoglobulins
D. Increased IgM with normal IgG
E. Increased IgG subclasses
Correct Answer: C. Markedly decreased immunoglobulins
X-linked agammaglobulinemia results from a defect in Bruton's
tyrosine kinase, preventing maturation of B lymphocytes. Patients
, have very low levels of mature B cells and all major
immunoglobulin classes, leading to recurrent infections with
encapsulated organisms.
6. A patient develops jaundice several days after receiving a
medication that causes oxidative stress. Blood smear
demonstrates Heinz bodies and bite cells. Which enzyme
deficiency is most likely?
A. Pyruvate kinase
B. Glucose-6-phosphate dehydrogenase
C. Hexokinase
D. Lactate dehydrogenase
E. Glutathione reductase
Correct Answer: B. Glucose-6-phosphate dehydrogenase
G6PD generates NADPH, which maintains glutathione in its
reduced form. Reduced glutathione protects erythrocytes from
oxidative injury. Deficiency can cause hemolysis after exposure to
oxidant drugs, infections, or certain foods.
7. Which phase of the cell cycle is primarily responsible for DNA
replication?
A. G1 phase
B. S phase
C. G2 phase
D. M phase
E. G0 phase
Correct Answer: B. S phase
COMPREHENSIVE REVIEW &
PRACTICE TEST EXAM QUESTIONS
WITH CORRECT ANSWERS PLUS
RATIONALES 2026/2027 EDITION
WITH INSTANT PDF DOWNLOAD
1. A 24-year-old man develops severe muscle cramps after
prolonged exercise in hot weather. Laboratory studies show an
elevated serum creatine kinase level. Which cellular structure is
primarily responsible for releasing calcium needed for skeletal
muscle contraction?
A. Golgi apparatus
B. Sarcoplasmic reticulum
C. Rough endoplasmic reticulum
D. Lysosome
E. Peroxisome
Correct Answer: B. Sarcoplasmic reticulum
The sarcoplasmic reticulum is a specialized form of smooth
endoplasmic reticulum that stores and releases calcium in
skeletal muscle. Depolarization triggers calcium release, allowing
calcium to bind troponin C and initiate actin-myosin interaction.
2. A newborn develops profound hypoglycemia, lactic acidosis,
and hepatomegaly after beginning feeds. Testing demonstrates
,impaired conversion of glucose-6-phosphate to free glucose.
Which enzyme is deficient?
A. Glucose-6-phosphatase
B. Pyruvate carboxylase
C. Glycogen phosphorylase
D. Hexokinase
E. Fructose-1,6-bisphosphatase
Correct Answer: A. Glucose-6-phosphatase
Glucose-6-phosphatase deficiency causes von Gierke disease, a
glycogen storage disorder characterized by severe fasting
hypoglycemia, lactic acidosis, hyperuricemia, hyperlipidemia,
and hepatomegaly. The enzyme is required for the final step of
both glycogenolysis and gluconeogenesis.
3. Which amino acid is most likely to be deficient in a patient
receiving a long-term parenteral nutrition regimen that lacks
adequate protein supplementation?
A. Tyrosine
B. Glutamine
C. Phenylalanine
D. Tryptophan
E. Methionine
Correct Answer: B. Glutamine
Glutamine is a major nitrogen donor and an important fuel source
for rapidly dividing cells, including enterocytes and immune cells.
During severe illness, it can become conditionally essential
because endogenous production may not meet metabolic
demands.
,4. A patient with chronic kidney disease develops normocytic
anemia. Which mechanism best explains this finding?
A. Increased hepcidin degradation
B. Reduced erythropoietin production
C. Increased red blood cell membrane synthesis
D. Increased intestinal iron absorption
E. Increased erythrocyte lifespan
Correct Answer: B. Reduced erythropoietin production
Renal peritubular interstitial cells normally produce
erythropoietin in response to tissue hypoxia. Chronic kidney
disease decreases erythropoietin production, resulting in
decreased erythrocyte production and a typically normocytic,
normochromic anemia.
5. A 19-year-old woman has recurrent infections with
encapsulated bacteria. Laboratory testing demonstrates absent
mature B cells. Which immunoglobulin abnormality is most
likely?
A. Increased IgE only
B. Isolated increased IgA
C. Markedly decreased immunoglobulins
D. Increased IgM with normal IgG
E. Increased IgG subclasses
Correct Answer: C. Markedly decreased immunoglobulins
X-linked agammaglobulinemia results from a defect in Bruton's
tyrosine kinase, preventing maturation of B lymphocytes. Patients
, have very low levels of mature B cells and all major
immunoglobulin classes, leading to recurrent infections with
encapsulated organisms.
6. A patient develops jaundice several days after receiving a
medication that causes oxidative stress. Blood smear
demonstrates Heinz bodies and bite cells. Which enzyme
deficiency is most likely?
A. Pyruvate kinase
B. Glucose-6-phosphate dehydrogenase
C. Hexokinase
D. Lactate dehydrogenase
E. Glutathione reductase
Correct Answer: B. Glucose-6-phosphate dehydrogenase
G6PD generates NADPH, which maintains glutathione in its
reduced form. Reduced glutathione protects erythrocytes from
oxidative injury. Deficiency can cause hemolysis after exposure to
oxidant drugs, infections, or certain foods.
7. Which phase of the cell cycle is primarily responsible for DNA
replication?
A. G1 phase
B. S phase
C. G2 phase
D. M phase
E. G0 phase
Correct Answer: B. S phase
