COMSAE Phase 1-Form ASA 123
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 24-year-old patient has a mutation affecting the beta-globin
gene, resulting in abnormal hemoglobin structure. The mutation
causes substitution of valine for glutamic acid at position 6 of the
beta chain. Which molecular mechanism best explains the disease
process?
A. Expansion of trinucleotide repeats causing abnormal protein folding
B. Single nucleotide substitution causing altered amino acid sequence
C. Deletion of an entire chromosome segment
D. Defective mitochondrial DNA replication
E. Abnormal RNA splicing of all globin genes
Answer: B. Single nucleotide substitution causing altered amino acid
sequence
The mutation responsible for sickle cell disease is a point mutation in
the beta-globin gene that changes glutamic acid to valine, producing
hemoglobin S. This is a missense mutation that alters protein structure
and function.
2. A patient with severe fasting hypoglycemia has increased
glycogen accumulation in hepatocytes. Laboratory testing shows
, impaired glucose-6-phosphatase activity. Which metabolic
pathway is primarily affected?
A. Glycolysis
B. Glycogenesis
C. Glycogenolysis with glucose release
D. Fatty acid oxidation
E. Ketone body formation
Answer: C. Glycogenolysis with glucose release
Glucose-6-phosphatase converts glucose-6-phosphate into free
glucose in the liver. Deficiency causes von Gierke disease, preventing
release of glucose during fasting and leading to hypoglycemia.
3. A researcher blocks sodium channels in a neuron. Which event
will be directly impaired?
A. Neurotransmitter synthesis
B. Action potential depolarization
C. Resting membrane potential maintenance
D. Calcium storage in the endoplasmic reticulum
E. Myelin production
Answer: B. Action potential depolarization
Voltage-gated sodium channels open during neuronal depolarization,
allowing sodium influx and generation of the action potential.
4. A patient develops prolonged bleeding after a minor injury.
Laboratory testing shows prolonged PT and a normal PTT. Which
coagulation pathway is most likely affected?
,A. Intrinsic pathway
B. Extrinsic pathway
C. Common pathway only
D. Platelet adhesion pathway
E. Fibrinolytic pathway
Answer: B. Extrinsic pathway
PT evaluates the extrinsic and common coagulation pathways. Factor
VII deficiency or vitamin K deficiency affecting factor VII can prolong
PT.
5. A medication inhibits acetylcholinesterase activity at the
neuromuscular junction. What is the expected effect?
A. Decreased acetylcholine concentration
B. Increased muscle relaxation
C. Prolonged acetylcholine activity
D. Blocked acetylcholine receptors
E. Reduced sodium influx into muscle cells
Answer: C. Prolonged acetylcholine activity
Acetylcholinesterase normally breaks down acetylcholine. Inhibition
increases acetylcholine levels and prolongs stimulation of nicotinic
receptors.
6. A patient with autoimmune destruction of pancreatic beta cells
develops hyperglycemia. Which hormone is deficient?
A. Glucagon
B. Cortisol
C. Insulin
, D. Growth hormone
E. Aldosterone
Answer: C. Insulin
Type 1 diabetes mellitus results from immune-mediated destruction of
pancreatic beta cells, causing decreased insulin secretion and
impaired glucose uptake.
7. A biopsy shows replacement of normal tissue with collagen after
injury. Which cell type is primarily responsible?
A. Neutrophils
B. Fibroblasts
C. Macrophages
D. Mast cells
E. Endothelial cells
Answer: B. Fibroblasts
Fibroblasts synthesize collagen and extracellular matrix components
during wound healing and fibrosis.
8. A child has recurrent bacterial infections due to inability to
produce antibodies. Which immune cell is defective?
A. T lymphocytes
B. Natural killer cells
C. B lymphocytes
D. Neutrophils
E. Macrophages
Answer: C. B lymphocytes
Foundational Biomedical Sciences Exam
Practice Questions & [Verified Answers],
Plus Explained Rationales|2026 Latest
Update| Instant Download PDF
1. A 24-year-old patient has a mutation affecting the beta-globin
gene, resulting in abnormal hemoglobin structure. The mutation
causes substitution of valine for glutamic acid at position 6 of the
beta chain. Which molecular mechanism best explains the disease
process?
A. Expansion of trinucleotide repeats causing abnormal protein folding
B. Single nucleotide substitution causing altered amino acid sequence
C. Deletion of an entire chromosome segment
D. Defective mitochondrial DNA replication
E. Abnormal RNA splicing of all globin genes
Answer: B. Single nucleotide substitution causing altered amino acid
sequence
The mutation responsible for sickle cell disease is a point mutation in
the beta-globin gene that changes glutamic acid to valine, producing
hemoglobin S. This is a missense mutation that alters protein structure
and function.
2. A patient with severe fasting hypoglycemia has increased
glycogen accumulation in hepatocytes. Laboratory testing shows
, impaired glucose-6-phosphatase activity. Which metabolic
pathway is primarily affected?
A. Glycolysis
B. Glycogenesis
C. Glycogenolysis with glucose release
D. Fatty acid oxidation
E. Ketone body formation
Answer: C. Glycogenolysis with glucose release
Glucose-6-phosphatase converts glucose-6-phosphate into free
glucose in the liver. Deficiency causes von Gierke disease, preventing
release of glucose during fasting and leading to hypoglycemia.
3. A researcher blocks sodium channels in a neuron. Which event
will be directly impaired?
A. Neurotransmitter synthesis
B. Action potential depolarization
C. Resting membrane potential maintenance
D. Calcium storage in the endoplasmic reticulum
E. Myelin production
Answer: B. Action potential depolarization
Voltage-gated sodium channels open during neuronal depolarization,
allowing sodium influx and generation of the action potential.
4. A patient develops prolonged bleeding after a minor injury.
Laboratory testing shows prolonged PT and a normal PTT. Which
coagulation pathway is most likely affected?
,A. Intrinsic pathway
B. Extrinsic pathway
C. Common pathway only
D. Platelet adhesion pathway
E. Fibrinolytic pathway
Answer: B. Extrinsic pathway
PT evaluates the extrinsic and common coagulation pathways. Factor
VII deficiency or vitamin K deficiency affecting factor VII can prolong
PT.
5. A medication inhibits acetylcholinesterase activity at the
neuromuscular junction. What is the expected effect?
A. Decreased acetylcholine concentration
B. Increased muscle relaxation
C. Prolonged acetylcholine activity
D. Blocked acetylcholine receptors
E. Reduced sodium influx into muscle cells
Answer: C. Prolonged acetylcholine activity
Acetylcholinesterase normally breaks down acetylcholine. Inhibition
increases acetylcholine levels and prolongs stimulation of nicotinic
receptors.
6. A patient with autoimmune destruction of pancreatic beta cells
develops hyperglycemia. Which hormone is deficient?
A. Glucagon
B. Cortisol
C. Insulin
, D. Growth hormone
E. Aldosterone
Answer: C. Insulin
Type 1 diabetes mellitus results from immune-mediated destruction of
pancreatic beta cells, causing decreased insulin secretion and
impaired glucose uptake.
7. A biopsy shows replacement of normal tissue with collagen after
injury. Which cell type is primarily responsible?
A. Neutrophils
B. Fibroblasts
C. Macrophages
D. Mast cells
E. Endothelial cells
Answer: B. Fibroblasts
Fibroblasts synthesize collagen and extracellular matrix components
during wound healing and fibrosis.
8. A child has recurrent bacterial infections due to inability to
produce antibodies. Which immune cell is defective?
A. T lymphocytes
B. Natural killer cells
C. B lymphocytes
D. Neutrophils
E. Macrophages
Answer: C. B lymphocytes
