Medical College Admission Test (MCAT)
– Advanced Practice Question Bank v2.0
150 Multiple-Choice Questions with
Correct Answers and Rationales a well
detailed one written and
graded A+ upgraded
SECTION 1: BIOLOGICAL AND BIOCHEMICAL FOUNDATIONS OF LIVING SYSTEMS (Questions 1–
40)
Question 1
A researcher is studying a metabolic pathway and discovers that a particular enzyme is inhibited
by the final product of the pathway. This type of regulation is best described as:
A) Competitive inhibition
B) Noncompetitive inhibition
C) Feedback inhibition
D) Allosteric activation
Correct Answer: C) Feedback inhibition
Rationale: Feedback inhibition occurs when the end product of a metabolic pathway inhibits an
enzyme early in the pathway, preventing overproduction. This is a common regulatory
mechanism in biosynthetic pathways.
,Question 2
Which of the following statements about the electron transport chain is CORRECT?
A) Complex I accepts electrons from FADH₂
B) Complex II pumps protons across the inner mitochondrial membrane
C) Cytochrome c is a mobile electron carrier
D) Oxygen is reduced to water at Complex III
Correct Answer: C) Cytochrome c is a mobile electron carrier
Rationale: Cytochrome c is a small, mobile protein that shuttles electrons between Complex III
and Complex IV. Complex I accepts electrons from NADH (not FADH₂), Complex II does not pump
protons, and oxygen is reduced to water at Complex IV.
Question 3
A patient presents with severe combined immunodeficiency (SCID) due to a deficiency in
adenosine deaminase (ADA). Which of the following best explains the pathophysiology?
A) Accumulation of adenosine triphosphate leading to impaired T-cell development
B) Accumulation of deoxyadenosine and dATP causing lymphocyte toxicity
C) Impaired antibody production due to B-cell deficiency only
D) Overproduction of purines leading to gout
Correct Answer: B) Accumulation of deoxyadenosine and dATP causing lymphocyte toxicity
Rationale: ADA deficiency leads to accumulation of deoxyadenosine, which is converted to
dATP. Elevated dATP inhibits ribonucleotide reductase, blocking DNA synthesis and causing
lymphocyte toxicity, resulting in SCID.
Question 4
In a cell undergoing meiosis, crossing over occurs during which phase?
A) Prophase I
B) Metaphase I
C) Prophase II
D) Metaphase II
Correct Answer: A) Prophase I
Rationale: Crossing over (recombination) occurs during prophase I of meiosis, specifically during
the pachytene stage when homologous chromosomes pair and exchange genetic material.
,Question 5
Which of the following correctly describes the role of the liver in carbohydrate metabolism?
A) The liver stores glycogen exclusively for its own use
B) The liver releases glucose into the bloodstream via gluconeogenesis and glycogenolysis
C) The liver cannot perform gluconeogenesis
D) The liver converts glucose to fatty acids for storage as glycogen
Correct Answer: B) The liver releases glucose into the bloodstream via gluconeogenesis and
glycogenolysis
Rationale: The liver maintains blood glucose homeostasis by releasing glucose through
glycogenolysis (breakdown of glycogen) and gluconeogenesis (synthesis from non-carbohydrate
precursors). Muscle glycogen is used only for muscle energy, not released into the bloodstream.
Question 6
A mutation in the promoter region of a gene would most likely affect:
A) The amino acid sequence of the protein
B) The rate of transcription of the gene
C) The splicing of mRNA
D) The stability of mRNA
Correct Answer: B) The rate of transcription of the gene
Rationale: The promoter is the region where RNA polymerase binds to initiate transcription.
Mutations in the promoter typically affect transcription efficiency (rate), not the coding
sequence, splicing, or mRNA stability.
Question 7
Which of the following lipoproteins is responsible for transporting endogenous triglycerides
from the liver to peripheral tissues?
A) Chylomicrons
B) VLDL
C) LDL
D) HDL
Correct Answer: B) VLDL
, Rationale: Very-low-density lipoproteins (VLDL) are produced by the liver and transport
endogenous triglycerides to peripheral tissues. Chylomicrons transport dietary (exogenous)
triglycerides; LDL transports cholesterol; HDL transports cholesterol from tissues back to the
liver.
Question 8
A researcher observes that a cell line has lost the ability to undergo apoptosis. Which of the
following proteins is most likely mutated?
A) Caspase-9
B) Cytochrome c
C) p53
D) All of the above
Correct Answer: D) All of the above
Rationale: Apoptosis requires multiple proteins: p53 activates the pathway, cytochrome c is
released from mitochondria, and caspase-9 is the initiator caspase in the intrinsic pathway.
Mutation in any could impair apoptosis.
Question 9
Which of the following amino acids would most likely be found on the surface of a protein,
interacting with water?
A) Alanine
B) Valine
C) Isoleucine
D) Serine
Correct Answer: D) Serine
Rationale: Serine is a polar, uncharged amino acid with a hydroxyl group that can form
hydrogen bonds with water, making it hydrophilic and likely to be found on the protein surface.
Alanine, valine, and isoleucine are nonpolar hydrophobic amino acids typically buried in the
protein interior.
Question 10
In the kidney, the majority of sodium reabsorption occurs in the:
– Advanced Practice Question Bank v2.0
150 Multiple-Choice Questions with
Correct Answers and Rationales a well
detailed one written and
graded A+ upgraded
SECTION 1: BIOLOGICAL AND BIOCHEMICAL FOUNDATIONS OF LIVING SYSTEMS (Questions 1–
40)
Question 1
A researcher is studying a metabolic pathway and discovers that a particular enzyme is inhibited
by the final product of the pathway. This type of regulation is best described as:
A) Competitive inhibition
B) Noncompetitive inhibition
C) Feedback inhibition
D) Allosteric activation
Correct Answer: C) Feedback inhibition
Rationale: Feedback inhibition occurs when the end product of a metabolic pathway inhibits an
enzyme early in the pathway, preventing overproduction. This is a common regulatory
mechanism in biosynthetic pathways.
,Question 2
Which of the following statements about the electron transport chain is CORRECT?
A) Complex I accepts electrons from FADH₂
B) Complex II pumps protons across the inner mitochondrial membrane
C) Cytochrome c is a mobile electron carrier
D) Oxygen is reduced to water at Complex III
Correct Answer: C) Cytochrome c is a mobile electron carrier
Rationale: Cytochrome c is a small, mobile protein that shuttles electrons between Complex III
and Complex IV. Complex I accepts electrons from NADH (not FADH₂), Complex II does not pump
protons, and oxygen is reduced to water at Complex IV.
Question 3
A patient presents with severe combined immunodeficiency (SCID) due to a deficiency in
adenosine deaminase (ADA). Which of the following best explains the pathophysiology?
A) Accumulation of adenosine triphosphate leading to impaired T-cell development
B) Accumulation of deoxyadenosine and dATP causing lymphocyte toxicity
C) Impaired antibody production due to B-cell deficiency only
D) Overproduction of purines leading to gout
Correct Answer: B) Accumulation of deoxyadenosine and dATP causing lymphocyte toxicity
Rationale: ADA deficiency leads to accumulation of deoxyadenosine, which is converted to
dATP. Elevated dATP inhibits ribonucleotide reductase, blocking DNA synthesis and causing
lymphocyte toxicity, resulting in SCID.
Question 4
In a cell undergoing meiosis, crossing over occurs during which phase?
A) Prophase I
B) Metaphase I
C) Prophase II
D) Metaphase II
Correct Answer: A) Prophase I
Rationale: Crossing over (recombination) occurs during prophase I of meiosis, specifically during
the pachytene stage when homologous chromosomes pair and exchange genetic material.
,Question 5
Which of the following correctly describes the role of the liver in carbohydrate metabolism?
A) The liver stores glycogen exclusively for its own use
B) The liver releases glucose into the bloodstream via gluconeogenesis and glycogenolysis
C) The liver cannot perform gluconeogenesis
D) The liver converts glucose to fatty acids for storage as glycogen
Correct Answer: B) The liver releases glucose into the bloodstream via gluconeogenesis and
glycogenolysis
Rationale: The liver maintains blood glucose homeostasis by releasing glucose through
glycogenolysis (breakdown of glycogen) and gluconeogenesis (synthesis from non-carbohydrate
precursors). Muscle glycogen is used only for muscle energy, not released into the bloodstream.
Question 6
A mutation in the promoter region of a gene would most likely affect:
A) The amino acid sequence of the protein
B) The rate of transcription of the gene
C) The splicing of mRNA
D) The stability of mRNA
Correct Answer: B) The rate of transcription of the gene
Rationale: The promoter is the region where RNA polymerase binds to initiate transcription.
Mutations in the promoter typically affect transcription efficiency (rate), not the coding
sequence, splicing, or mRNA stability.
Question 7
Which of the following lipoproteins is responsible for transporting endogenous triglycerides
from the liver to peripheral tissues?
A) Chylomicrons
B) VLDL
C) LDL
D) HDL
Correct Answer: B) VLDL
, Rationale: Very-low-density lipoproteins (VLDL) are produced by the liver and transport
endogenous triglycerides to peripheral tissues. Chylomicrons transport dietary (exogenous)
triglycerides; LDL transports cholesterol; HDL transports cholesterol from tissues back to the
liver.
Question 8
A researcher observes that a cell line has lost the ability to undergo apoptosis. Which of the
following proteins is most likely mutated?
A) Caspase-9
B) Cytochrome c
C) p53
D) All of the above
Correct Answer: D) All of the above
Rationale: Apoptosis requires multiple proteins: p53 activates the pathway, cytochrome c is
released from mitochondria, and caspase-9 is the initiator caspase in the intrinsic pathway.
Mutation in any could impair apoptosis.
Question 9
Which of the following amino acids would most likely be found on the surface of a protein,
interacting with water?
A) Alanine
B) Valine
C) Isoleucine
D) Serine
Correct Answer: D) Serine
Rationale: Serine is a polar, uncharged amino acid with a hydroxyl group that can form
hydrogen bonds with water, making it hydrophilic and likely to be found on the protein surface.
Alanine, valine, and isoleucine are nonpolar hydrophobic amino acids typically buried in the
protein interior.
Question 10
In the kidney, the majority of sodium reabsorption occurs in the:
