COMSAE Phase 1 Form 114
Comprehensive Basic Medical Sciences
Practice Examination Question And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
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Question 1
A 23-year-old man has severe muscle weakness after prolonged exercise. Lab
studies show failure of ATP-dependent calcium reuptake in muscle. Which
structure is primarily responsible?
A. Sarcolemma
B. Sarcoplasmic reticulum
C. Mitochondria
D. T-tubules
Rationale: The sarcoplasmic reticulum stores and releases calcium in skeletal
muscle. During relaxation, ATP-dependent Ca²⁺-ATPase pumps return calcium
into the SR. Failure leads to impaired relaxation and weakness. The sarcolemma
conducts impulses, mitochondria produce ATP but are not primary Ca storage,
and T-tubules transmit depolarization.
Question 2
,A drug inhibits bacterial protein synthesis by binding the 50S ribosomal subunit.
What is the most likely mechanism?
A. Blocking tRNA binding to mRNA
B. Inhibiting DNA gyrase
C. Preventing peptide bond formation/translocation
D. Blocking folate synthesis
Rationale: 50S inhibitors (macrolides, clindamycin) block translocation or
peptide elongation. DNA gyrase inhibitors affect DNA replication, folate
inhibitors affect nucleotide synthesis, and tRNA binding is primarily 30S-related.
Question 3
Which immunoglobulin is the first produced in a primary immune response?
A. IgA
B. IgG
C. IgM
D. IgE
Rationale: IgM is the first antibody produced due to its pentameric structure
allowing strong early agglutination. IgG dominates secondary responses, IgA
mucosal immunity, and IgE allergic responses.
Question 4
A patient has decreased TSH and increased free T4. Where is the primary
pathology?
A. Thyroid gland
B. Pituitary adenoma
C. Hypothalamus
D. Primary hyperthyroidism feedback suppression
,Rationale: Elevated T4 suppresses TSH via negative feedback, indicating primary
thyroid overproduction (e.g., Graves disease). Pituitary/hypothalamic causes
would show inappropriately normal or elevated TSH.
Question 5
Which enzyme converts angiotensin I to angiotensin II?
A. Renin
B. Aldosterone synthase
C. ACE2
D. Angiotensin-converting enzyme (ACE)
Rationale: ACE in pulmonary endothelium converts angiotensin I to II, causing
vasoconstriction and aldosterone release. Renin converts angiotensinogen to
angiotensin I.
Question 6
A mutation impairs beta-oxidation of fatty acids. Which organelle is affected?
A. Endoplasmic reticulum
B. Ribosomes
C. Mitochondria
D. Golgi apparatus
Rationale: Beta-oxidation occurs in mitochondria, producing acetyl-CoA. ER is
involved in lipid synthesis, ribosomes in protein synthesis, and Golgi in protein
modification.
Question 7
Which neurotransmitter is decreased in Parkinson disease?
, A. Serotonin
B. GABA
C. Acetylcholine
D. Dopamine
Rationale: Parkinson disease involves degeneration of substantia nigra
dopaminergic neurons, reducing dopamine in basal ganglia pathways.
Question 8
Which condition is associated with decreased FEV1/FVC ratio?
A. Pulmonary fibrosis
B. Sarcoidosis
C. Asthma
D. Pleural effusion
Rationale: Obstructive diseases (asthma) reduce FEV1 more than FVC, lowering
ratio. Restrictive diseases increase or preserve ratio.
Question 9
Which structure filters blood plasma in the kidney?
A. Collecting duct
B. Loop of Henle
C. Distal tubule
D. Glomerulus
Rationale: The glomerulus performs ultrafiltration through fenestrated
capillaries into Bowman’s capsule.
Question 10
Which vitamin deficiency causes scurvy?
Comprehensive Basic Medical Sciences
Practice Examination Question And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
Question 1
A 23-year-old man has severe muscle weakness after prolonged exercise. Lab
studies show failure of ATP-dependent calcium reuptake in muscle. Which
structure is primarily responsible?
A. Sarcolemma
B. Sarcoplasmic reticulum
C. Mitochondria
D. T-tubules
Rationale: The sarcoplasmic reticulum stores and releases calcium in skeletal
muscle. During relaxation, ATP-dependent Ca²⁺-ATPase pumps return calcium
into the SR. Failure leads to impaired relaxation and weakness. The sarcolemma
conducts impulses, mitochondria produce ATP but are not primary Ca storage,
and T-tubules transmit depolarization.
Question 2
,A drug inhibits bacterial protein synthesis by binding the 50S ribosomal subunit.
What is the most likely mechanism?
A. Blocking tRNA binding to mRNA
B. Inhibiting DNA gyrase
C. Preventing peptide bond formation/translocation
D. Blocking folate synthesis
Rationale: 50S inhibitors (macrolides, clindamycin) block translocation or
peptide elongation. DNA gyrase inhibitors affect DNA replication, folate
inhibitors affect nucleotide synthesis, and tRNA binding is primarily 30S-related.
Question 3
Which immunoglobulin is the first produced in a primary immune response?
A. IgA
B. IgG
C. IgM
D. IgE
Rationale: IgM is the first antibody produced due to its pentameric structure
allowing strong early agglutination. IgG dominates secondary responses, IgA
mucosal immunity, and IgE allergic responses.
Question 4
A patient has decreased TSH and increased free T4. Where is the primary
pathology?
A. Thyroid gland
B. Pituitary adenoma
C. Hypothalamus
D. Primary hyperthyroidism feedback suppression
,Rationale: Elevated T4 suppresses TSH via negative feedback, indicating primary
thyroid overproduction (e.g., Graves disease). Pituitary/hypothalamic causes
would show inappropriately normal or elevated TSH.
Question 5
Which enzyme converts angiotensin I to angiotensin II?
A. Renin
B. Aldosterone synthase
C. ACE2
D. Angiotensin-converting enzyme (ACE)
Rationale: ACE in pulmonary endothelium converts angiotensin I to II, causing
vasoconstriction and aldosterone release. Renin converts angiotensinogen to
angiotensin I.
Question 6
A mutation impairs beta-oxidation of fatty acids. Which organelle is affected?
A. Endoplasmic reticulum
B. Ribosomes
C. Mitochondria
D. Golgi apparatus
Rationale: Beta-oxidation occurs in mitochondria, producing acetyl-CoA. ER is
involved in lipid synthesis, ribosomes in protein synthesis, and Golgi in protein
modification.
Question 7
Which neurotransmitter is decreased in Parkinson disease?
, A. Serotonin
B. GABA
C. Acetylcholine
D. Dopamine
Rationale: Parkinson disease involves degeneration of substantia nigra
dopaminergic neurons, reducing dopamine in basal ganglia pathways.
Question 8
Which condition is associated with decreased FEV1/FVC ratio?
A. Pulmonary fibrosis
B. Sarcoidosis
C. Asthma
D. Pleural effusion
Rationale: Obstructive diseases (asthma) reduce FEV1 more than FVC, lowering
ratio. Restrictive diseases increase or preserve ratio.
Question 9
Which structure filters blood plasma in the kidney?
A. Collecting duct
B. Loop of Henle
C. Distal tubule
D. Glomerulus
Rationale: The glomerulus performs ultrafiltration through fenestrated
capillaries into Bowman’s capsule.
Question 10
Which vitamin deficiency causes scurvy?
