MCAT Cheat Sheet

20 Standard Amino Acids — Side Chain Families

Nonpolar (hydrophobic): Gly (G), Ala (A), Val (V), Leu (L), Ile (I), Met (M), Pro (P), Phe (F), Trp (W)

Polar uncharged: Ser (S), Thr (T), Tyr (Y), Cys (C), Asn (N), Gln (Q)

Acidic (negative @ pH 7): Asp (D), Glu (E)

Basic (positive @ pH 7): Lys (K), Arg (R), His (H)

pI = (pKa1 + pKa2) / 2 for neutral side chains; include side-chain pKa for charged residues.

Glycolysis (cytosol, 10 steps, net 2 ATP + 2 NADH)

Glucose → 2 pyruvate, ΔG ≈ −85 kJ/mol

Key regulated steps:

• Hexokinase / Glucokinase (Step 1) — Glc→G6P, ATP→ADP
• PFK-1 (Step 3) — F6P→F1,6BP, rate-limiting; activated by AMP/F2,6BP, inhibited by ATP/citrate
• Pyruvate kinase (Step 10) — PEP→pyruvate, ATP made

Krebs cycle (mito matrix, per acetyl-CoA)

Net: 3 NADH + 1 FADH₂ + 1 GTP + 2 CO₂

Order: citrate → isocitrate → α-KG → succinyl-CoA → succinate → fumarate → malate → OAA

Decarboxylations: isocitrate → α-KG (NADH + CO₂) and α-KG → succinyl-CoA (NADH + CO₂)

Enzyme kinetics — Michaelis-Menten

v = V_max[S] / (K_m + [S])

Lineweaver-Burk: 1/v = (K_m/V_max)(1/[S]) + 1/V_max

Inhibition shifts:

Kinematics (1-D, constant a)

v = v₀ + at

x = x₀ + v₀t + ½at²

v² = v₀² + 2a(x − x₀)

x = ½(v + v₀)t

g = 9.8 m/s² downward (use 10 m/s² for MCAT estimation)

Energy + Momentum

KE = ½mv²

PE_grav = mgh

PE_spring = ½kx²

p = mv ; F = dp/dt = ma

Work-energy: W = ΔKE = F·d cos θ

Elastic collision: KE + p conserved · Inelastic: p only.

Thermodynamics

ΔG = ΔH − TΔS

ΔG° = −RT ln K = −nFE°

Spontaneity: ΔG < 0

1st law: ΔU = q + w (gas work: w = −PΔV)

Acids / bases / pH

pH = −log[H⁺] · K_w = 10⁻¹⁴

pH + pOH = 14

Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA])

Buffer: max capacity at pH = pKa (±1).

Strong acids: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄.

Optics — single-lens equation

1/f = 1/d_o + 1/d_i

m = h_i/h_o = −d_i/d_o

Sign convention: + when on same side as incoming light (real); − virtual.

Snell's law: n₁ sin θ₁ = n₂ sin θ₂

Common functional groups (Org Chem)

Memory model (Atkinson-Shiffrin)

Sensory → STM (≈7±2 items, 30s) → LTM

• LTM types: Explicit (semantic, episodic) · Implicit (procedural, priming)
• Encoding: rote rehearsal → maintenance; elaborative rehearsal → deeper
• Retrieval: recall > recognition; state/context-dependent

Operant vs. Classical Conditioning

Classical (Pavlov): UCS → UCR; pair NS + UCS → CS → CR

Operant (Skinner): behavior → consequence

Schedules: variable-ratio is most resistant to extinction.

Psychological disorders (DSM-5 highlights)

• Anxiety: GAD, panic, specific phobia, social anxiety, separation
• Mood: MDD (≥2 wk), bipolar I (≥1 manic), persistent depressive
• Psychotic: schizophrenia (+/− symptoms ≥6 mo)
• Personality: A (odd) / B (dramatic, ASPD/BPD/HPD/NPD) / C (anxious)

Sociology — group behavior

• Conformity: Asch line study (normative + informational)
• Obedience: Milgram (65% to lethal shock)
• Bystander effect: Genovese; diffusion of responsibility
• Group polarization: opinions intensify after group discussion
• Groupthink: consensus over realism (Bay of Pigs)

Passage strategy (Kaplan)

1. Preview first sentence, last sentence, structure tags
2. Read for main idea + author's tone (not detail)
3. Distill a 5-word summary per paragraph in the margin
4. Outline the passage as you go

Question types

• Comprehension: main idea, scope, detail
• Reasoning within text: assumption, inference, definition-in-context
• Reasoning beyond text: application, strengthen, weaken, analogy

Eliminate distractors: Faulty Use of Detail · Out of Scope · Opposite · Distortion

Rhetorical signal words

Continuation: moreover, furthermore, in addition

Contrast: however, although, yet, but, despite

Cause/effect: because, thus, therefore, since

Conclusion: in summary, in conclusion, ultimately

Evidence: for example, for instance, illustrates

Physical constants

Greek letters (MCAT)

SI prefixes (powers of 10)