Medical College Admission Test (MCAT) Exam
by AAMC New 2025-2026 Version with All
Questions and 100% Correct Answers and
Rationale
MCAT Practice Test: 70 Questions
Section 1: Biological and Biochemical Foundations of Living Systems (BBLS)(20 questions,
~29% of test)
Question 1 (Discrete: Biochemistry)Which enzyme catalyzes the rate-limiting step in glycolysis?
A. Hexokinase
B. Phosphofructokinase-1
C. Pyruvate kinase
D. Aldolase Correct Answer: B
Rationale: Phosphofructokinase-1 (PFK-1) is the rate-limiting enzyme in glycolysis, converting
fructose-6-phosphate to fructose-1,6-bisphosphate.
Question 2 (Passage-Based: Biology)Passage: A researcher studies a mutation in hemoglobin
that reduces oxygen affinity. Patients exhibit fatigue and cyanosis.
What is the likely effect of this mutation on the oxygen-hemoglobin dissociation curve?
A. Shift to the left
B. Shift to the right
C. No change
D. Increased slope Correct Answer: B
Rationale: Reduced oxygen affinity shifts the dissociation curve to the right, indicating
hemoglobin releases oxygen more readily, consistent with fatigue and cyanosis.
Question 3 (Discrete: Genetics)A couple has a child with cystic fibrosis (autosomal recessive).
What is the probability their next child will have the disease if both are carriers?
A. 0%
B. 25%
C. 50%
D. 75% Correct Answer: B
Rationale: For an autosomal recessive disorder, two carrier parents (Aa × Aa) have a 25% chance
(aa) of producing an affected child.
Question 4 (Passage-Based: Biochemistry)Passage: An enzyme’s activity is measured at varying
pH levels, peaking at pH 7.4.
What does this suggest about the enzyme’s optimal environment?
A. Acidic
B. Neutral
, C. Basic
D. Denatured Correct Answer: B
Rationale: A pH of 7.4 is near neutral, indicating the enzyme functions optimally in a
physiological environment.
Question 5 (Discrete: Physiology)Which hormone regulates blood calcium by increasing bone
resorption?
A. Calcitonin
B. Parathyroid hormone
C. Insulin
D. Glucagon Correct Answer: B
Rationale: Parathyroid hormone increases blood calcium by stimulating osteoclasts for bone
resorption.
Question 6 (Passage-Based: Microbiology)Passage: A bacterial strain grows optimally at 37°C
but not at 50°C.
What type of bacterium is this?
A. Thermophile
B. Mesophile
C. Psychrophile
D. Hyperthermophile Correct Answer: B
Rationale: Mesophiles grow best at moderate temperatures (20–45°C), such as 37°C, typical for
human pathogens.
Question 7 (Discrete: Molecular Biology)What is the role of mRNA in protein synthesis?
A. Catalyzes peptide bond formation
B. Carries amino acids to ribosomes
C. Transcribes DNA to RNA
D. Serves as a template for translation Correct Answer: D
Rationale: mRNA carries the genetic code from DNA to ribosomes for translation into proteins.
Question 8 (Passage-Based: Cell Biology)Passage: A cell culture shows increased apoptosis after
UV exposure.
What organelle is primarily involved in initiating apoptosis?
A. Nucleus
B. Mitochondria
C. Endoplasmic reticulum
D. Golgi apparatus Correct Answer: B
Rationale: Mitochondria release cytochrome c, triggering the intrinsic pathway of apoptosis.
Question 9 (Discrete: Immunology)Which cells produce antibodies in response to an antigen?
A. T-helper cells
B. B cells
C. Natural killer cells
D. Macrophages Correct Answer: B
Rationale: B cells differentiate into plasma cells that produce antibodies specific to antigens.
by AAMC New 2025-2026 Version with All
Questions and 100% Correct Answers and
Rationale
MCAT Practice Test: 70 Questions
Section 1: Biological and Biochemical Foundations of Living Systems (BBLS)(20 questions,
~29% of test)
Question 1 (Discrete: Biochemistry)Which enzyme catalyzes the rate-limiting step in glycolysis?
A. Hexokinase
B. Phosphofructokinase-1
C. Pyruvate kinase
D. Aldolase Correct Answer: B
Rationale: Phosphofructokinase-1 (PFK-1) is the rate-limiting enzyme in glycolysis, converting
fructose-6-phosphate to fructose-1,6-bisphosphate.
Question 2 (Passage-Based: Biology)Passage: A researcher studies a mutation in hemoglobin
that reduces oxygen affinity. Patients exhibit fatigue and cyanosis.
What is the likely effect of this mutation on the oxygen-hemoglobin dissociation curve?
A. Shift to the left
B. Shift to the right
C. No change
D. Increased slope Correct Answer: B
Rationale: Reduced oxygen affinity shifts the dissociation curve to the right, indicating
hemoglobin releases oxygen more readily, consistent with fatigue and cyanosis.
Question 3 (Discrete: Genetics)A couple has a child with cystic fibrosis (autosomal recessive).
What is the probability their next child will have the disease if both are carriers?
A. 0%
B. 25%
C. 50%
D. 75% Correct Answer: B
Rationale: For an autosomal recessive disorder, two carrier parents (Aa × Aa) have a 25% chance
(aa) of producing an affected child.
Question 4 (Passage-Based: Biochemistry)Passage: An enzyme’s activity is measured at varying
pH levels, peaking at pH 7.4.
What does this suggest about the enzyme’s optimal environment?
A. Acidic
B. Neutral
, C. Basic
D. Denatured Correct Answer: B
Rationale: A pH of 7.4 is near neutral, indicating the enzyme functions optimally in a
physiological environment.
Question 5 (Discrete: Physiology)Which hormone regulates blood calcium by increasing bone
resorption?
A. Calcitonin
B. Parathyroid hormone
C. Insulin
D. Glucagon Correct Answer: B
Rationale: Parathyroid hormone increases blood calcium by stimulating osteoclasts for bone
resorption.
Question 6 (Passage-Based: Microbiology)Passage: A bacterial strain grows optimally at 37°C
but not at 50°C.
What type of bacterium is this?
A. Thermophile
B. Mesophile
C. Psychrophile
D. Hyperthermophile Correct Answer: B
Rationale: Mesophiles grow best at moderate temperatures (20–45°C), such as 37°C, typical for
human pathogens.
Question 7 (Discrete: Molecular Biology)What is the role of mRNA in protein synthesis?
A. Catalyzes peptide bond formation
B. Carries amino acids to ribosomes
C. Transcribes DNA to RNA
D. Serves as a template for translation Correct Answer: D
Rationale: mRNA carries the genetic code from DNA to ribosomes for translation into proteins.
Question 8 (Passage-Based: Cell Biology)Passage: A cell culture shows increased apoptosis after
UV exposure.
What organelle is primarily involved in initiating apoptosis?
A. Nucleus
B. Mitochondria
C. Endoplasmic reticulum
D. Golgi apparatus Correct Answer: B
Rationale: Mitochondria release cytochrome c, triggering the intrinsic pathway of apoptosis.
Question 9 (Discrete: Immunology)Which cells produce antibodies in response to an antigen?
A. T-helper cells
B. B cells
C. Natural killer cells
D. Macrophages Correct Answer: B
Rationale: B cells differentiate into plasma cells that produce antibodies specific to antigens.
