Physics and biology together represent a significant portion of the MCAT sciences. The key to doing well is understanding conceptual relationships, not just memorizing formulas.
MCAT Physics: What Is and Isn't Tested
MCAT physics focuses on concepts that apply to biology and medicine: fluids, electricity (circuits with biological analogues), optics, waves, mechanics, and thermodynamics. Calculus is not required. All problems can be solved with algebra. The key is understanding which equation applies to which situation.
Fluids: The Most MCAT-Relevant Physics Topic
The cardiovascular system is modeled as a fluid system. Understanding fluid dynamics is clinically relevant and highly tested.
- Pressure: P = F/A. In fluids: P = ρgh (hydrostatic pressure)
- Continuity equation: A₁v₁ = A₂v₂ — as a vessel narrows, velocity increases
- Bernoulli's equation: Increased velocity → decreased pressure (explains why stenotic vessels can cause problems)
- Poiseuille's Law: Flow ∝ r⁴/L×η — radius has the most dramatic effect on flow rate
Electricity and Circuits (With Biological Relevance)
The nervous system uses electrical signaling. Ohm's Law (V=IR), series vs. parallel circuits, and capacitance appear frequently with biological framings.
- Series circuits: same current, voltages add. Total resistance = R₁ + R₂
- Parallel circuits: same voltage, currents add. 1/R_total = 1/R₁ + 1/R₂
- The membrane functions as a capacitor — know this analogy
Optics: Lenses and the Eye
The thin lens equation (1/f = 1/do + 1/di) and magnification (M = -di/do) are high yield. Converging lenses have positive focal length; diverging have negative. Myopia (nearsighted) corrected with diverging lens; hyperopia (farsighted) with converging lens.
MCAT Biology: The High-Yield Topics
Cell biology
- Eukaryotic organelles and their functions — know the endomembrane system in detail
- Cell cycle phases and checkpoints — CDK/cyclin regulation
- Apoptosis pathways — intrinsic (mitochondrial) vs. extrinsic (death receptor)
Genetics and molecular biology
- DNA replication: leading vs. lagging strand, enzymes involved (helicase, primase, DNA pol III, ligase)
- Transcription and translation: know the steps and where each occurs
- Gene regulation in prokaryotes: lac operon (inducible), trp operon (repressible)
- Inheritance patterns: Mendelian, X-linked, autosomal recessive/dominant, codominance
Lab techniques (high yield)
| Technique | What it does |
|---|---|
| PCR | Amplifies specific DNA sequences exponentially |
| Gel electrophoresis | Separates DNA/protein by size — smaller moves farther |
| ELISA | Detects specific proteins using antibodies — used in HIV testing |
| Western blot | Confirms specific protein presence — confirmatory HIV test |
| Southern/Northern blot | Southern = DNA, Northern = RNA detection |
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