MCAT 2026 Practice Exam: Biology, Chemistry, Psychology & CARS |
200 Questions with Verified Answers & Rationales | INSTANT PDF
DOWNLOAD
MCAT 2026 practice exam. This document contains 200 multiple-choice questions designed to mirror the
style, difficulty, and breadth of the actual MCAT. You will encounter questions from Biology/Biochemistry,
Chemistry/Physics, Psychology/Sociology, and Critical Analysis & Reasoning Skills (CARS). Each question is
followed by the correct answer and a concise rationale. Use this exam to assess your knowledge, identify
weak areas, and build stamina.
Key Topics Covered
• Biology/Biochemistry – Cellular structure & function, metabolism, molecular biology, genetics, human
physiology, evolution & diversity
• Chemistry/Physics – General chemistry (atomic structure, periodic trends, stoichiometry,
thermochemistry, kinetics, equilibrium, acids/bases, electrochemistry), organic chemistry, physics
(kinematics, forces, energy, waves, fluids, electricity, magnetism, optics)
• Psychology/Sociology – Sensation & perception, learning & memory, cognition, motivation, emotion,
personality, psychological disorders, social structure, demography, inequality
• CARS – Reading comprehension, reasoning within and beyond the text, analysis of arguments, tone,
purpose, rhetorical devices
Biology (Questions 1–60)
1. Which organelle is primarily responsible for ATP production in eukaryotic cells?
A) Nucleus
B) Mitochondrion
C) Ribosome
D) Golgi apparatus
Answer B: Mitochondrion
Rationale: Mitochondria perform oxidative phosphorylation to produce ATP. Nucleus stores DNA,
ribosomes synthesize proteins, Golgi modifies/sorts proteins.
2. A patient has a deficiency in parietal cells. Which of the following would be most directly impaired?
A) Digestion of carbohydrates
B) Absorption of vitamin B12
,C) Emulsification of fats
D) Secretion of pancreatic lipase
Answer B: Absorption of vitamin B12
Rationale: Parietal cells secrete intrinsic factor needed for B12 absorption. Carbohydrate digestion involves
amylase, fat emulsification involves bile, lipase is pancreatic.
3. In the lac operon, when lactose is present and glucose is absent, which of the following occurs?
A) Repressor binds the operator; CAP is inactive
B) Repressor is inactive; CAP activates transcription
C) Repressor binds the operator; CAP activates transcription
D) Repressor is inactive; CAP is inactive
Answer B: Repressor is inactive; CAP activates transcription
Rationale: Lactose inactivates repressor; low glucose increases cAMP, activating CAP which enhances RNA
polymerase binding. Transcription is maximal.
4. A man with blood type AB (IAIB) and a woman with type O (ii) have a child. What is the probability
the child will have type A blood?
A) 0%
B) 25%
C) 50%
D) 100%
Answer C: 50%
Rationale: Man contributes either IA or IB; woman contributes i. Child can be IAi (type A) or IBi (type B)
with equal probability. Type O impossible.
5. Which of the following hormones is secreted by the posterior pituitary?
A) Growth hormone
B) Antidiuretic hormone (ADH)
C) Thyroid-stimulating hormone
D) Prolactin
Answer B: Antidiuretic hormone (ADH)
Rationale: Posterior pituitary stores and releases ADH and oxytocin (made in hypothalamus). Others are
from anterior pituitary.
,6. During skeletal muscle contraction, calcium ions bind to which protein?
A) Actin
B) Myosin
C) Troponin
D) Tropomyosin
Answer C: Troponin
Rationale: Ca2+ binds troponin C, causing conformational change that moves tropomyosin, exposing
myosin-binding sites on actin.
7. A point mutation changes a codon from UAC (tyrosine) to UAG. What type of mutation is this?
A) Silent
B) Missense
C) Nonsense
D) Frameshift
Answer C: Nonsense
Rationale: UAG is a stop codon, causing premature termination of translation. Tyrosine to stop = nonsense
mutation.
8. Which of the following best describes the role of the enzyme telomerase?
A) Synthesizes RNA primers during replication
B) Extends telomeres to prevent shortening
C) Unwinds DNA ahead of the replication fork
D) Removes RNA primers and fills gaps
Answer B: Extends telomeres to prevent shortening
Rationale: Telomerase adds repetitive DNA sequences to chromosome ends, compensating for end-
replication problem. Active in germ cells and some stem cells.
9. In the kidney, most reabsorption of water and solutes occurs in the:
A) Glomerulus
B) Proximal convoluted tubule
C) Loop of Henle
, D) Collecting duct
Answer B: Proximal convoluted tubule
Rationale: PCT reabsorbs ~65% of filtered water, Na+, glucose, amino acids via active and passive
processes. Glomerulus filters only.
10. Which of the following is an example of negative feedback in homeostasis?
A) Oxytocin release during childbirth increasing contractions
B) Insulin secretion in response to high blood glucose
C) Blood clotting cascade amplifying itself
D) Action potential depolarization opening more Na+ channels
Answer B: Insulin secretion in response to high blood glucose
Rationale: Insulin lowers glucose, reversing the stimulus – negative feedback. A, C, D are positive feedback.
11. A diploid organism has 2n = 16 chromosomes. How many chromatids are present during
metaphase II of meiosis?
A) 8
B) 16
C) 32
D) 64
Answer B: 16
Rationale: After meiosis I, cells are haploid (n=8). Each chromosome still has two sister chromatids, so
chromatid count = 8 × 2 = 16.
12. Which of the following statements about enzyme kinetics is true for a competitive inhibitor?
A) Decreases Vmax and increases Km
B) Increases Km but Vmax unchanged
C) Decreases Vmax and Km unchanged
D) Increases both Vmax and Km
Answer B: Increases Km but Vmax unchanged
Rationale: Competitive inhibitor binds active site, raising substrate concentration needed for half-max rate
(Km↑). At high substrate, Vmax is still reached.
200 Questions with Verified Answers & Rationales | INSTANT PDF
DOWNLOAD
MCAT 2026 practice exam. This document contains 200 multiple-choice questions designed to mirror the
style, difficulty, and breadth of the actual MCAT. You will encounter questions from Biology/Biochemistry,
Chemistry/Physics, Psychology/Sociology, and Critical Analysis & Reasoning Skills (CARS). Each question is
followed by the correct answer and a concise rationale. Use this exam to assess your knowledge, identify
weak areas, and build stamina.
Key Topics Covered
• Biology/Biochemistry – Cellular structure & function, metabolism, molecular biology, genetics, human
physiology, evolution & diversity
• Chemistry/Physics – General chemistry (atomic structure, periodic trends, stoichiometry,
thermochemistry, kinetics, equilibrium, acids/bases, electrochemistry), organic chemistry, physics
(kinematics, forces, energy, waves, fluids, electricity, magnetism, optics)
• Psychology/Sociology – Sensation & perception, learning & memory, cognition, motivation, emotion,
personality, psychological disorders, social structure, demography, inequality
• CARS – Reading comprehension, reasoning within and beyond the text, analysis of arguments, tone,
purpose, rhetorical devices
Biology (Questions 1–60)
1. Which organelle is primarily responsible for ATP production in eukaryotic cells?
A) Nucleus
B) Mitochondrion
C) Ribosome
D) Golgi apparatus
Answer B: Mitochondrion
Rationale: Mitochondria perform oxidative phosphorylation to produce ATP. Nucleus stores DNA,
ribosomes synthesize proteins, Golgi modifies/sorts proteins.
2. A patient has a deficiency in parietal cells. Which of the following would be most directly impaired?
A) Digestion of carbohydrates
B) Absorption of vitamin B12
,C) Emulsification of fats
D) Secretion of pancreatic lipase
Answer B: Absorption of vitamin B12
Rationale: Parietal cells secrete intrinsic factor needed for B12 absorption. Carbohydrate digestion involves
amylase, fat emulsification involves bile, lipase is pancreatic.
3. In the lac operon, when lactose is present and glucose is absent, which of the following occurs?
A) Repressor binds the operator; CAP is inactive
B) Repressor is inactive; CAP activates transcription
C) Repressor binds the operator; CAP activates transcription
D) Repressor is inactive; CAP is inactive
Answer B: Repressor is inactive; CAP activates transcription
Rationale: Lactose inactivates repressor; low glucose increases cAMP, activating CAP which enhances RNA
polymerase binding. Transcription is maximal.
4. A man with blood type AB (IAIB) and a woman with type O (ii) have a child. What is the probability
the child will have type A blood?
A) 0%
B) 25%
C) 50%
D) 100%
Answer C: 50%
Rationale: Man contributes either IA or IB; woman contributes i. Child can be IAi (type A) or IBi (type B)
with equal probability. Type O impossible.
5. Which of the following hormones is secreted by the posterior pituitary?
A) Growth hormone
B) Antidiuretic hormone (ADH)
C) Thyroid-stimulating hormone
D) Prolactin
Answer B: Antidiuretic hormone (ADH)
Rationale: Posterior pituitary stores and releases ADH and oxytocin (made in hypothalamus). Others are
from anterior pituitary.
,6. During skeletal muscle contraction, calcium ions bind to which protein?
A) Actin
B) Myosin
C) Troponin
D) Tropomyosin
Answer C: Troponin
Rationale: Ca2+ binds troponin C, causing conformational change that moves tropomyosin, exposing
myosin-binding sites on actin.
7. A point mutation changes a codon from UAC (tyrosine) to UAG. What type of mutation is this?
A) Silent
B) Missense
C) Nonsense
D) Frameshift
Answer C: Nonsense
Rationale: UAG is a stop codon, causing premature termination of translation. Tyrosine to stop = nonsense
mutation.
8. Which of the following best describes the role of the enzyme telomerase?
A) Synthesizes RNA primers during replication
B) Extends telomeres to prevent shortening
C) Unwinds DNA ahead of the replication fork
D) Removes RNA primers and fills gaps
Answer B: Extends telomeres to prevent shortening
Rationale: Telomerase adds repetitive DNA sequences to chromosome ends, compensating for end-
replication problem. Active in germ cells and some stem cells.
9. In the kidney, most reabsorption of water and solutes occurs in the:
A) Glomerulus
B) Proximal convoluted tubule
C) Loop of Henle
, D) Collecting duct
Answer B: Proximal convoluted tubule
Rationale: PCT reabsorbs ~65% of filtered water, Na+, glucose, amino acids via active and passive
processes. Glomerulus filters only.
10. Which of the following is an example of negative feedback in homeostasis?
A) Oxytocin release during childbirth increasing contractions
B) Insulin secretion in response to high blood glucose
C) Blood clotting cascade amplifying itself
D) Action potential depolarization opening more Na+ channels
Answer B: Insulin secretion in response to high blood glucose
Rationale: Insulin lowers glucose, reversing the stimulus – negative feedback. A, C, D are positive feedback.
11. A diploid organism has 2n = 16 chromosomes. How many chromatids are present during
metaphase II of meiosis?
A) 8
B) 16
C) 32
D) 64
Answer B: 16
Rationale: After meiosis I, cells are haploid (n=8). Each chromosome still has two sister chromatids, so
chromatid count = 8 × 2 = 16.
12. Which of the following statements about enzyme kinetics is true for a competitive inhibitor?
A) Decreases Vmax and increases Km
B) Increases Km but Vmax unchanged
C) Decreases Vmax and Km unchanged
D) Increases both Vmax and Km
Answer B: Increases Km but Vmax unchanged
Rationale: Competitive inhibitor binds active site, raising substrate concentration needed for half-max rate
(Km↑). At high substrate, Vmax is still reached.
