MCAT practice questions and exam guide

Which intermolecular force is strongest between molecules of water?

1. London dispersion
2. Dipole-dipole
3. Hydrogen bonding
4. Ion-dipole

Answer: C — Hydrogen bonding

Water molecules H-bond strongly: each O can accept 2 H-bonds and each O-H can donate 1, giving water its high boiling point, high specific heat, and surface tension. H-bonding is a special, particularly strong dipole-dipole interaction limited to N, O, F bonded to H.

A society undergoing rapid urbanization, declining traditional kinship ties, and increased division of labor, per Durkheim, is moving from:

1. Mechanical to organic solidarity
2. Organic to mechanical solidarity
3. Capitalism to feudalism
4. Gemeinschaft to no solidarity at all

Answer: A — Mechanical to organic solidarity

A) Correct: mechanical (premodern, similarity-based) → organic (modern, interdependence). B) Reverses direction. C) Marxian materialism in reverse. D) Durkheim said organic replaces, not eliminates, cohesion.

A Michaelis–Menten enzyme kinetics equation is:

1. v = k · t
2. v = (Vmax · [S]) / (Km + [S]) — Km is substrate concentration at half-Vmax; reflects apparent affinity
3. v = Vmax always
4. v = Vmax / [S]

Answer: B — v = (Vmax · [S]) / (Km + [S]) — Km is substrate concentration at half-Vmax; reflects apparent affinity

B) Defining equation. A/C/D) Each is incorrect.

Which type of memory is impaired in classic Alzheimer's disease early in the course?

1. Procedural memory (how to ride a bike)
2. Sensory memory
3. Semantic memory only
4. Episodic / declarative memory (recent events)

Answer: D — Episodic / declarative memory (recent events)

Early Alzheimer's typically impairs episodic memory (recent events, conversations, where keys were placed) first, due to hippocampal pathology. Procedural memory (A) — motor skills — is preserved longer because it depends on basal ganglia and cerebellum. Late-stage AD affects nearly all memory systems.

When light passes from air (n = 1.0) into water (n = 1.33), the light:

1. Speeds up and bends away from the normal
2. Slows down and bends toward the normal (denser medium → smaller angle from normal)
3. Reflects entirely
4. Travels at the same speed

Answer: B — Slows down and bends toward the normal (denser medium → smaller angle from normal)

Snell's law: n₁ sin θ₁ = n₂ sin θ₂. Going to denser medium → smaller angle, slower speed (v = c/n).

Competitive inhibition of an enzyme affects:

1. Vmax but not Km
2. Neither
3. Both Vmax and Km
4. Km but not Vmax (Km appears to increase; Vmax unchanged with sufficient substrate)

Answer: D — Km but not Vmax (Km appears to increase; Vmax unchanged with sufficient substrate)

Competitive inhibitors increase apparent Km (need more substrate to reach half-Vmax) but Vmax is preserved by adding enough substrate. Noncompetitive inhibitors decrease Vmax without changing Km.

Which assumption is most necessary for the argument: 'Because online courses cost less than in-person courses, universities should expand online offerings'?

1. That cost reduction is a desirable goal that should outweigh other considerations like educational quality
2. That online courses are always better
3. That all students prefer online learning
4. That universities have unlimited budgets

Answer: A — That cost reduction is a desirable goal that should outweigh other considerations like educational quality

A) Correct: argument from cost to action must assume cost matters more than trade-offs. B) Too strong. C) Universal preference isn't required. D) Unlimited budgets would undermine cost-saving as a motive.

Working memory has a typical capacity of:

1. 1-2 items
2. 100+ items
3. Unlimited
4. 4-7 items at a time (Cowan/Miller; can be expanded by chunking)

Answer: D — 4-7 items at a time (Cowan/Miller; can be expanded by chunking)

Miller's 'magical number 7 ± 2' described span; more recent work (Cowan) places working memory capacity at around 4 items. Chunking expands functional capacity.

The four MCAT sections are:

1. Chemical and Physical Foundations; CARS; Biological and Biochemical Foundations; Psychological, Social, and Biological Foundations of Behavior
2. Math, English, Physics, History
3. Anatomy, Patient Care, Ethics, Research
4. USMLE Step 1 topics alone

Answer: A — Chemical and Physical Foundations; CARS; Biological and Biochemical Foundations; Psychological, Social, and Biological Foundations of Behavior

A) AAMC's four sections. B/C/D) Each is incorrect.

Carbohydrate digestion begins in:

1. The stomach
2. The mouth (via salivary amylase)
3. The small intestine only
4. The large intestine

Answer: B — The mouth (via salivary amylase)

Salivary amylase initiates starch digestion in the mouth. Stomach acid inactivates it; pancreatic amylase resumes digestion in the small intestine, where final brush-border enzymes complete the process.

The primary structure of a protein refers to:

1. Its three-dimensional shape
2. The linear amino acid sequence — defined by peptide bonds
3. Quaternary aggregation
4. Disulfide bridges only

Answer: B — The linear amino acid sequence — defined by peptide bonds

B) Defining concept. A/C/D) Each is a different level.

A reflex arc is best described as:

1. Voluntary movement controlled by the cerebrum
2. A pathway generated entirely in the cortex
3. A neural pathway involving sensory neuron → spinal interneuron → motor neuron, producing a rapid response without direct cortical involvement
4. A pathway triggered by hormones alone

Answer: C — A neural pathway involving sensory neuron → spinal interneuron → motor neuron, producing a rapid response without direct cortical involvement

C) Classical reflex anatomy. A/B/D) Each misstates.

Acid-base in physiology?

Bicarbonate buffer maintains blood pH 7.35-7.45. CO₂ + H₂O ↔ H₂CO₃ ↔ HCO₃⁻ + H⁺.

Punnett square Aa × Aa: ratio?

1 AA : 2 Aa : 1 aa. Phenotype: 3:1.

Kinematic: x = ?

x = v₀t + ½at².

Erikson's stages: focus on?

Psychosocial development through 8 stages from infancy to old age.

Centripetal force?

F_c = mv²/r.

Michaelis-Menten kinetics?

V = (Vmax · [S])/(Km + [S]). Km = [S] at half Vmax.