MCAT EXAM AND PRACTICE EXAM NEWEST 2026/ 2027
TEST BANK| MEDICAL COLLEGE ADMISSION TEST AAMC
EXAM PREP WITH COMPLETE 400 QUESTIONS AND
CORRECT VERIFIED ANSWERS/ ALREADY GRADED A+
Question 1 – Chemical & Physical Foundations: Enzyme Kinetics
An enzyme follows Michaelis-Menten kinetics with Km = 5 mM and Vmax = 100 μmol/min. A
competitive inhibitor is added at a concentration equal to 3× its Ki.
Question: What effect does this inhibitor have on the apparent Km and Vmax?
A) Km increases; Vmax unchanged
B) Km unchanged; Vmax decreases
C) Km increases; Vmax decreases
D) Km unchanged; Vmax unchanged
Correct Answer: A
Explanation: Competitive inhibitors bind the active site and can be overcome by substrate. They
increase apparent Km (lower apparent affinity) but do not change Vmax because saturating
substrate displaces the inhibitor. B describes noncompetitive inhibition; C describes
mixed/uncompetitive; D is no inhibition.
Question 2 – Chemical & Physical Foundations: Acid-Base
A patient's blood pH is 7.28, PCO₂ is 30 mmHg, and HCO₃⁻ is 14 mEq/L.
Question: Which acid-base disturbance is present?
A) Respiratory acidosis
B) Respiratory alkalosis
C) Metabolic acidosis
D) Metabolic alkalosis
Correct Answer: C
,Explanation: Low pH indicates acidosis. Low HCO₃⁻ (normal ~24) indicates a metabolic cause.
The low PCO₂ reflects respiratory compensation (hyperventilation). A would show elevated
PCO₂; B would show elevated pH; D would show elevated pH and HCO₃⁻.
Question 3 – Biological & Biochemical Foundations: Genetics
A woman who is a carrier for an X-linked recessive disorder has children with an unaffected
man.
Question: What is the probability that a son will be affected?
A) 0%
B) 25%
C) 50%
D) 100%
Correct Answer: C
Explanation: Sons receive their X chromosome from the mother. A carrier mother has one
affected X and one normal X, so each son has a 50% chance of inheriting the affected allele.
Daughters would have a 50% chance of being carriers but would generally be unaffected. A is
wrong because the mother carries the allele; B confuses overall offspring probability with son-
specific probability; D would require an affected mother.
Question 4 – Psychological, Social & Biological Foundations: Learning
A rat learns to press a lever to avoid a mild foot shock. After several sessions, the shock is
discontinued, but the rat continues pressing the lever.
Question: This behavior best illustrates:
A) Positive reinforcement
B) Negative reinforcement
C) Punishment
D) Extinction
Correct Answer: B
Explanation: Negative reinforcement increases behavior by removing an aversive stimulus (the
shock). Positive reinforcement (A) adds a rewarding stimulus. Punishment (C) decreases
, behavior. Extinction (D) would be the eventual decrease in lever pressing once the shock no
longer follows.
Question 5 – Biological & Biochemical Foundations: Metabolism
During prolonged starvation, the brain begins to use which fuel source to spare glucose for the
central nervous system?
A) Free fatty acids
B) Ketone bodies
C) Lactate
D) Amino acids
Correct Answer: B
Explanation: After glycogen depletion, the liver produces ketone bodies (β-hydroxybutyrate,
acetoacetate) from fatty acid oxidation. The brain adapts to use ketones, reducing glucose
demand. Free fatty acids (A) cannot cross the blood-brain barrier efficiently. Lactate (C) is used
during intense exercise, not prolonged starvation. Amino acids (D) are gluconeogenic substrates
but not the primary brain fuel.
Question 6 – Chemical & Physical Foundations: Optics
A convex lens has a focal length of 10 cm. An object is placed 15 cm from the lens.
Question: Where is the image formed?
A) 6 cm on the opposite side
B) 10 cm on the opposite side
C) 30 cm on the opposite side
D) 30 cm on the same side
Correct Answer: C
Explanation: Using 1/f = 1/do + 1/di: 1/10 = 1/15 + 1/di → 1/di = 1/10 − 1/15 = 1/30 → di = 30
cm. The positive sign indicates a real image on the opposite side. A would result from incorrect
algebra; B ignores the object distance; D would indicate a virtual image (diverging lens or object
inside focal point).
Question 7 – Psychological, Social & Biological Foundations: Sociology
TEST BANK| MEDICAL COLLEGE ADMISSION TEST AAMC
EXAM PREP WITH COMPLETE 400 QUESTIONS AND
CORRECT VERIFIED ANSWERS/ ALREADY GRADED A+
Question 1 – Chemical & Physical Foundations: Enzyme Kinetics
An enzyme follows Michaelis-Menten kinetics with Km = 5 mM and Vmax = 100 μmol/min. A
competitive inhibitor is added at a concentration equal to 3× its Ki.
Question: What effect does this inhibitor have on the apparent Km and Vmax?
A) Km increases; Vmax unchanged
B) Km unchanged; Vmax decreases
C) Km increases; Vmax decreases
D) Km unchanged; Vmax unchanged
Correct Answer: A
Explanation: Competitive inhibitors bind the active site and can be overcome by substrate. They
increase apparent Km (lower apparent affinity) but do not change Vmax because saturating
substrate displaces the inhibitor. B describes noncompetitive inhibition; C describes
mixed/uncompetitive; D is no inhibition.
Question 2 – Chemical & Physical Foundations: Acid-Base
A patient's blood pH is 7.28, PCO₂ is 30 mmHg, and HCO₃⁻ is 14 mEq/L.
Question: Which acid-base disturbance is present?
A) Respiratory acidosis
B) Respiratory alkalosis
C) Metabolic acidosis
D) Metabolic alkalosis
Correct Answer: C
,Explanation: Low pH indicates acidosis. Low HCO₃⁻ (normal ~24) indicates a metabolic cause.
The low PCO₂ reflects respiratory compensation (hyperventilation). A would show elevated
PCO₂; B would show elevated pH; D would show elevated pH and HCO₃⁻.
Question 3 – Biological & Biochemical Foundations: Genetics
A woman who is a carrier for an X-linked recessive disorder has children with an unaffected
man.
Question: What is the probability that a son will be affected?
A) 0%
B) 25%
C) 50%
D) 100%
Correct Answer: C
Explanation: Sons receive their X chromosome from the mother. A carrier mother has one
affected X and one normal X, so each son has a 50% chance of inheriting the affected allele.
Daughters would have a 50% chance of being carriers but would generally be unaffected. A is
wrong because the mother carries the allele; B confuses overall offspring probability with son-
specific probability; D would require an affected mother.
Question 4 – Psychological, Social & Biological Foundations: Learning
A rat learns to press a lever to avoid a mild foot shock. After several sessions, the shock is
discontinued, but the rat continues pressing the lever.
Question: This behavior best illustrates:
A) Positive reinforcement
B) Negative reinforcement
C) Punishment
D) Extinction
Correct Answer: B
Explanation: Negative reinforcement increases behavior by removing an aversive stimulus (the
shock). Positive reinforcement (A) adds a rewarding stimulus. Punishment (C) decreases
, behavior. Extinction (D) would be the eventual decrease in lever pressing once the shock no
longer follows.
Question 5 – Biological & Biochemical Foundations: Metabolism
During prolonged starvation, the brain begins to use which fuel source to spare glucose for the
central nervous system?
A) Free fatty acids
B) Ketone bodies
C) Lactate
D) Amino acids
Correct Answer: B
Explanation: After glycogen depletion, the liver produces ketone bodies (β-hydroxybutyrate,
acetoacetate) from fatty acid oxidation. The brain adapts to use ketones, reducing glucose
demand. Free fatty acids (A) cannot cross the blood-brain barrier efficiently. Lactate (C) is used
during intense exercise, not prolonged starvation. Amino acids (D) are gluconeogenic substrates
but not the primary brain fuel.
Question 6 – Chemical & Physical Foundations: Optics
A convex lens has a focal length of 10 cm. An object is placed 15 cm from the lens.
Question: Where is the image formed?
A) 6 cm on the opposite side
B) 10 cm on the opposite side
C) 30 cm on the opposite side
D) 30 cm on the same side
Correct Answer: C
Explanation: Using 1/f = 1/do + 1/di: 1/10 = 1/15 + 1/di → 1/di = 1/10 − 1/15 = 1/30 → di = 30
cm. The positive sign indicates a real image on the opposite side. A would result from incorrect
algebra; B ignores the object distance; D would indicate a virtual image (diverging lens or object
inside focal point).
Question 7 – Psychological, Social & Biological Foundations: Sociology
