MCAT Master Vocabulary – Comprehensive Quick-Review

120 high-yield MCAT vocabulary flashcards spanning general chemistry, organic chemistry, biochemistry, biology, physics, psychology, and sociology. Review each term–definition pair to reinforce foundational concepts quickly and efficiently.

Absolute Configuration (R/S)

System that assigns each chiral center an R (clockwise) or S (counter-clockwise) arrangement based on Cahn-Ingold-Prelog priorities.

Acetyl-CoA

Two-carbon thioester formed from pyruvate, fatty acids, or amino acids; enters the citric-acid cycle or serves as building block for lipid synthesis.

Activation Energy (Ea)

Minimum amount of energy that reacting molecules must possess for a collision to result in a chemical reaction.

Active Transport

Movement of molecules across a membrane against their electrochemical gradient, requiring energy input (ATP or coupled ion gradient).

Aldol Condensation

Base- or acid-catalyzed reaction in which an enolate ion attacks a carbonyl carbon, forming β-hydroxy carbonyl products that may dehydrate to α,β-unsaturated carbonyls.

Allosteric Enzyme

Enzyme whose activity is regulated by binding of effector molecules at sites other than the active site, producing conformational changes.

Ampere (A)

SI base unit of electric current; 1 A equals flow of 1 coulomb of charge per second.

Amphipathic

Describes a molecule containing both hydrophilic (polar) and hydrophobic (non-polar) regions (e.g., phospholipids).

Anhydride

Carboxylic acid derivative formed by condensation of two acids with loss of water; high-energy acyl transfer reagent.

Antinode

Point of maximum displacement in a standing wave.

Arrhenius Acid

Species that increases [H⁺] when dissolved in aqueous solution.

Atomic Number (Z)

Number of protons in the nucleus of an atom; uniquely identifies an element.

Avogadro’s Number (Nₐ)

6.022 × 10²³ particles per mole; converts between atomic-scale and macroscopic amounts.

Beta Decay (β⁻)

Radioactive process where a neutron converts to a proton with emission of an electron and antineutrino.

Bohr Model

Early atomic model describing electrons moving in fixed circular orbits with quantized energies around the nucleus.

Buffer Solution

A mixture of weak acid/base and its conjugate salt that resists pH changes upon small additions of strong acid or base.

Cation

Positively charged ion produced by loss of electrons.

Centromere

Constricted region of a chromosome that joins sister chromatids and attaches to spindle fibers during mitosis/meiosis.

Charles’s Law

For a fixed amount of gas at constant pressure, volume is directly proportional to absolute temperature (V ∝ T).

Chiral Center

Tetrahedral carbon atom bonded to four different substituents, giving rise to non-superimposable mirror images.

Competitive Inhibitor

Molecule that binds to an enzyme’s active site and increases Km while leaving Vmax unchanged.

Complement System

Series of plasma proteins that, when activated, enhance innate and adaptive immune responses by opsonization and cell lysis.

Conjugation (Organic)

Alternating single and multiple bonds that allow π-electron delocalization across adjacent aligned p-orbitals, stabilizing the molecule.

Coulomb’s Law

Force between two point charges is F = k|q₁q₂|/r², attractive for opposite signs and repulsive for like charges.

Cross-Over (Meiosis)

Exchange of genetic material between homologous chromosomes during prophase I, increasing genetic diversity.

Dalton’s Law of Partial Pressures

Total pressure of a gas mixture equals the sum of individual partial pressures of component gases.

Deoxyribose

Five-carbon sugar lacking an oxygen at the 2′ position; found in DNA nucleotides.

Determinant of Capacitance

For a parallel-plate capacitor, C = ε₀A/d; depends on plate area, separation, and dielectric constant.

Diffraction

Bending and spreading of waves when they encounter an obstacle or pass through a narrow slit comparable to wavelength.

Disulfide Bond

Covalent linkage between two cysteine residues (–S–S–) that stabilizes tertiary and quaternary protein structure.

Electrolyte

Substance that dissociates into ions in solution, thereby conducting electricity.

Electron Affinity

Energy change when an atom gains an electron to form an anion; increases toward upper right of periodic table.

Endergonic Reaction

Non-spontaneous process with positive ΔG requiring input of free energy.

Enolate

Resonance-stabilized anion formed by deprotonation of an α-hydrogen adjacent to a carbonyl; acts as nucleophile.

Entropy (S)

Thermodynamic measure of system disorder or energy dispersal; increases for spontaneous processes.

Epinephrine

Catecholamine hormone produced by adrenal medulla; mediates sympathetic fight-or-flight responses, increasing heart rate and blood glucose.

Equivalence Point

In titration, stage at which stoichiometrically equivalent moles of titrant and analyte have reacted.

Faraday’s Constant (F)

Magnitude of electric charge per mole of electrons, approximately 96 485 C mol⁻¹.

Fischer Projection

Two-dimensional representation of stereochemistry where vertical lines go back (dashes) and horizontal lines come forward (wedges).

Fluorescence

Emission of visible light as a molecule relaxes from an excited singlet state back to ground state after photon absorption.

Flux (Magnetic)

Product of magnetic field strength and area perpendicular to the field; measured in weber (Wb).

Free Radical

Atom or molecule containing an unpaired electron, making it highly reactive.

G Protein-Coupled Receptor (GPCR)

Seven-transmembrane cell-surface receptor that activates heterotrimeric G proteins, triggering second-messenger cascades.

Galvanic (Voltaic) Cell

Electrochemical cell in which a spontaneous redox reaction produces electrical energy (E°cell > 0).

Gamete

Haploid reproductive cell (sperm or ovum) produced via meiosis; fusion of two gametes forms a zygote.

Ganglion

Cluster of neuronal cell bodies located outside the central nervous system.

Glomerulus

Network of capillaries in the kidney where blood plasma is filtered into Bowman’s capsule to form filtrate.

Glycogen Synthase

Key regulated enzyme that catalyzes formation of α-1,4 glycosidic bonds during glycogenesis.

Glycolysis

Ten-step anaerobic pathway in cytosol converting glucose to pyruvate, producing net 2 ATP and 2 NADH per glucose.

Grignard Reagent

Organomagnesium halide (RMgX) that acts as strong nucleophile to form carbon–carbon bonds with electrophiles.

Ground State

Lowest energy electronic configuration of an atom or molecule.

Half-Life (t½)

Time required for half the nuclei in a radioactive sample to decay or for half of a reactant to be consumed.

Haworth Projection

Planar drawing depicting cyclic monosaccharide rings with orientation of substituents.

Heisenberg Uncertainty Principle

Fundamental limit stating that position and momentum of a particle cannot both be precisely known simultaneously (Δx·Δp ≥ ħ/2).

Henry’s Law

Solubility of a gas in a liquid is directly proportional to the gas’s partial pressure above the liquid (C = kH·P).

Hess’s Law

Overall enthalpy change for a reaction equals sum of enthalpy changes for individual steps; state-function property.

Homeostasis

Maintenance of stable internal physiological conditions by self-regulating processes.

Homologous Chromosomes

Pair of chromosomes, one from each parent, carrying the same genes in the same order but possibly different alleles.

Hydrogen Bond

Strong dipole-dipole attraction between a hydrogen atom bonded to N, O or F and a lone pair on another electronegative atom.

Hyperbola (Physics)

Shape of inverse (1/r²) relationships such as Coulombic or gravitational potential graphs.

Immunoglobulin (Antibody)

Y-shaped protein produced by B cells that specifically binds antigens to neutralize or mark them for destruction.

Induction (Organic)

Electron withdrawal or donation through σ bonds due to electronegativity differences, influencing reactivity and acidity.

Inertia

Property of mass to resist changes in velocity; quantified by mass in Newton’s first law.

Isoelectric Point (pI)

pH at which an amino acid or protein carries no net electric charge.

Isosbestic Point

Wavelength at which absorbance of two species crossing in a spectrophotometric titration are equal, indicating only two species present.

Ketogenesis

Formation of ketone bodies (acetoacetate, β-hydroxybutyrate, acetone) from acetyl-CoA in liver during prolonged fasting.

Kinetic Product

Reaction product that forms fastest under low-temperature, irreversible conditions; often less stable than thermodynamic product.

Laplace’s Law (Alveoli)

Pressure inside a spherical surface P = 2γ/r; explains surfactant’s role in reducing alveolar surface tension.

Le Châtelier’s Principle

If a dynamic equilibrium is disturbed, the system shifts to counteract the disturbance and restore equilibrium.

Ligase

Enzyme that joins two biomolecules (usually DNA fragments) using ATP hydrolysis.

Lineweaver–Burk Plot

Double-reciprocal graph (1/V vs 1/[S]) linearizing Michaelis-Menten kinetics; intercepts yield 1/Vmax and –1/Km.

Logarithm (base 10)

Inverse of exponentiation; log₁₀(x) equals the power to which 10 must be raised to obtain x.

Magnetic Field (B)

Vector field exerting magnetic forces on moving charges and magnetic dipoles; units tesla (T).

Mass Defect

Difference between predicted sum of nucleon masses and actual nucleus mass; converted to binding energy via E = mc².

Michaelis Constant (Km)

Substrate concentration at which an enzyme operates at half its maximal velocity; indicator of substrate affinity.

Micelle

Spherical aggregate of surfactant molecules in aqueous solution with hydrophobic cores and hydrophilic shells.

Mutarotation

Spontaneous interconversion between α- and β-anomers of a sugar through the open-chain form, changing optical rotation.

Nernst Equation

Relates cell potential to standard potential and reaction quotient: E = E° – (0.0592 V/n) log Q at 298 K.

Node (Standing Wave)

Point along a standing wave where displacement is always zero.

Northern Blot

Laboratory technique that detects specific RNA sequences separated by gel electrophoresis via labeled probes.

Nucleophile

Electron-rich species that donates a lone pair to form a bond; “nucleus-loving.”

Osmotic Pressure (π)

Pressure required to prevent water movement across a semipermeable membrane; π = iMRT.

Oxidative Phosphorylation

Coupling of the electron-transport chain–generated proton gradient to ATP synthesis by ATP synthase in mitochondria.

Paramagnetic

Atom or molecule with unpaired electrons that is attracted to an external magnetic field.

Pascal’s Principle

A change in pressure applied to an incompressible fluid is transmitted undiminished throughout the fluid.

Peptide Bond

Amide linkage between carboxyl group of one amino acid and amino group of another; exhibits partial double-bond character.

pKa

Negative logarithm of acid dissociation constant; lower pKa indicates stronger acid.

Plasmid

Small circular extrachromosomal DNA molecule in bacteria that replicates independently and may carry antibiotic resistance genes.

Poiseuille’s Law

Describes laminar flow rate Q = πr⁴ΔP/8ηL through a cylindrical pipe; highlights strong dependence on radius.

Polarimeter

Instrument that measures optical rotation of chiral compounds to determine concentration or enantiomeric purity.

Power (Physics)

Rate of energy transfer or work done per unit time; P = W/t; SI unit watt (W).

Precision

Degree to which repeated measurements yield similar results; reproducibility (not the same as accuracy).

Primer (DNA)

Short nucleic acid sequence providing a free 3′-OH for DNA polymerase initiation during replication or PCR.

Prostaglandin

Paracrine/autocrine eicosanoid signaling molecules derived from arachidonic acid that regulate inflammation, vasodilation, fever, etc.

Protic Solvent

Solvent capable of hydrogen bonding (e.g., water, alcohols); stabilizes charged intermediates and affects reaction mechanisms.

Purification (Protein)

Isolation of a single protein from a complex mixture using techniques such as chromatography and electrophoresis.

Quantum Number n

Principal quantum number indicating electron energy level/shell; larger n means higher energy and larger radius.

Radioactive Decay Constant (λ)

Probability per unit time that a nucleus will decay; related to half-life t½ = ln2/λ.

Raoult’s Law

Vapor-pressure depression of solvent by solute: Psolution = Χsolvent·P°solvent.

Reducing Sugar

Carbohydrate with a free anomeric carbon capable of acting as a reducing agent (e.g., glucose, lactose).