Preparatory Sciences Core Syllabus: Physics, Biology, and Chemistry

Vocabulary practice cards providing definitions for core laws, structural components, and mechanisms from the physics, biology, and chemistry syllabi.

Stevin's Law

The hydrostatic law stating that the pressure exerted by an incompressible liquid increases linearly with depth according to the formula $P = P_0 + \rho g h$, where $\rho$ is density, $g$ is gravitational acceleration, and $h$ is depth.

Pascal's Principle

The physical law stating that any change in pressure applied to an enclosed, incompressible fluid is transmitted undiminished and uniformly in all directions throughout the entire fluid.

Archimedes' Principle

The hydrostatic principle stating that a body immersed entirely or partially in a fluid experiences an upward buoyant force equal in magnitude to the weight of the fluid displaced by the body.

Equation of Continuity

A fluid dynamics relation based on conservation of mass for an ideal, incompressible fluid stating that the product of the cross-sectional area and flow velocity remains constant along a streamline ($A_1 v_1 = A_2 v_2$).

Bernoulli's Theorem

A fluid dynamics principle expressing energy conservation for steady, non-viscous flow along a streamline, establishing that the sum of static pressure, dynamic pressure, and potential energy per unit volume is constant ($P + \frac{1}{2}\rho v^2 + \rho g h = \text{constant}$).

Poiseuille's Law

The physical relationship describing laminar, steady flow of a viscous fluid through a cylindrical tube, stating that volume flow rate is directly proportional to the pressure gradient and the fourth power of the radius, and inversely proportional to length and dynamic viscosity.

Laplace's Law (Curvature Pressure)

A formula describing the pressure difference across a curved fluid interface or hollow organ wall as directly proportional to the surface tension and inversely proportional to the radius of curvature.

Inverse Square Law (Wave Intensity)

The physical law stating that the intensity of a wave propagating spherically from a point source decreases proportionally to the square of the distance from that source ($I \propto \frac{1}{r^2}$).

Doppler Effect

The observed change in the frequency or pitch of a wave resulting from relative motion between the emitting source and the observer.

First Law of Thermodynamics

The law of energy conservation for thermodynamic systems, stating that the change in internal energy ($\Delta U$) is equal to the net heat exchanged ($Q$) minus the work done by the system ($W$): $\Delta U = Q - W$.

Carnot Cycle

An idealized, fully reversible thermodynamic cycle consisting of two isothermal and two adiabatic processes, which defines the maximum theoretical efficiency achievable by any heat engine operating between two temperatures.

Entropy

A thermodynamic state function that quantifies the degree of irreversibility and microscopic disorder or multiplicity of accessible microstates in a system, dictating the spontaneous direction of natural processes ($\Delta S_{\text{universe}} \ge 0$).

Coulomb's Law

The fundamental law of electrostatics stating that the magnitude of the electrostatic force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

Joule Effect

The phenomenon wherein electrical energy is irreversibly converted into thermal energy due to resistance when an electric current flows through a conductor, with power dissipated given by $P = I^2 R$.

Lorentz Force

The force exerted on a charged particle moving through an electromagnetic field, given vectorially by $\mathbf{F} = q(\mathbf{E} + \mathbf{v} \times \mathbf{B})$.

Faraday-Neumann-Lenz Law

The law of electromagnetic induction stating that the induced electromotive force in a circuit equals the negative rate of change of magnetic flux through that circuit, with the induced current flowing in a direction that opposes the flux change.

Lambert-Beer Law

The optical relation stating that the absorbance of light passing through a absorbing solution is directly proportional to both the molar absorptivity coefficient, the path length of the light beam, and the solute concentration.

Horizontal Gene Transfer

The non-genealogical transmission of genetic material between distinct organisms, occurring in bacteria primarily via transformation (uptake of free DNA), conjugation (plasmid transfer via pilus), and transduction (bacteriophage-mediated transfer).

Endosymbiotic Theory

The evolutionary model proposing that eukaryotic organelles, specifically mitochondria and plastids, originated from free-living prokaryotic cells engulfed by an ancestral host cell.

Nucleosome

The basic repeating structural unit of eukaryotic chromatin, composed of approximately $146$ base pairs of DNA wound around an octamer of core histone proteins ($\text{H2A}$, $\text{H2B}$, $\text{H3}$, and $\text{H4}$).

Okazaki Fragments

Short, newly synthesized DNA fragments produced discontinuously on the lagging template strand during replication, initiated by RNA primers and subsequently joined by DNA ligase.

Telomerase

A ribonucleoprotein reverse transcriptase enzyme that synthesizes telomeric repeat sequences onto the ends of linear chromosomes, counteracting chromosome shortening and replicative senescence.

Lac Operon

An inducible operon model in prokaryotes responsible for the transport and metabolism of lactose, regulated transcriptionally by a repressor protein and cyclic AMP receptor protein (CRP).

Spliceosome

A dynamic ribonucleoprotein complex consisting of small nuclear RNAs (snRNAs) and proteins that removes non-coding introns from precursor messenger RNA (pre-mRNA) and splices coding exons together.

Epistasis

A genetic phenomenon in which the phenotypic expression of an allele at one gene locus is altered, masked, or suppressed by alleles at a completely different gene locus.

Genomic Imprinting

An epigenetic phenomenon causing genes to be expressed in a parent-of-origin-specific manner through differential DNA methylation and chromatin modification.

Translocon

A membrane-bound protein-conducting channel (such as the Sec61 complex) located in the endoplasmic reticulum membrane that translocates nascent polypeptides from ribosomes into the ER lumen.

SNARE Proteins

A large family of transmembrane proteins (v-SNAREs and t-SNAREs) that mediate vesicle targeting, docking, and membrane fusion between transport vesicles and their target cellular compartments.

Mannose-6-Phosphate (M6P)

A specialized carbohydrate modification added in the Golgi complex that targets newly synthesized acid hydrolase enzymes specifically to the lysosomal compartment.

Mitophagy

The specialized, selective degradation of dysfunctional or surplus mitochondria by macroautophagy to maintain cellular metabolic integrity.

Mechanotransduction

The cellular process by which external physical forces and mechanical signals from the extracellular matrix are converted into biochemical and intracellular signals via adhesion receptors like integrins.

Restriction Point (R Point)

A critical checkpoint in the late $G_1$ phase of the eukaryotic cell cycle at which a cell commits irreversibly to entering the S phase and undergoing division, regulated by cyclin D-CDK4/6 and Rb phosphorylation.

APC/C (Anaphase-Promoting Complex/Cyclosome)

An E3 ubiquitin ligase that targets specific cell-cycle regulators, notably securin and mitotic cyclins, for proteasomal degradation, thereby triggering sister chromatid separation and exit from mitosis.

MOMP (Mitochondrial Outer Membrane Permeabilization)

The key commitment event in the intrinsic pathway of apoptosis, mediated by pro-apoptotic BCL-2 family proteins, which releases cytochrome c from the intermembrane space into the cytosol to activate the apoptosome.

Pauli Exclusion Principle

A quantum mechanical principle stating that no two identical fermions, such as electrons, can occupy the exact same quantum state simultaneously, meaning no two electrons in an atom can have the same four quantum numbers.

Hund's Rule

A rule of atomic physics stating that every orbital in a degenerate subshell is singly occupied with electrons having parallel spins before any one orbital is doubly occupied.

Henry's Law

The gas law establishing that at a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with the liquid ($C = k_{\text{H}} P$).

Raoult's Law

A colligative property law stating that the partial vapor pressure of each volatile component in an ideal mixture is equal to the vapor pressure of the pure component multiplied by its mole fraction in the solution ($P_A = X_A P_A^\circ$).

van 't Hoff Factor ($i$)

A measure of the effect of a solute on colligative properties, defined as the ratio of the actual concentration of particles produced when the substance dissolves to the concentration of the substance calculated from its mass.

Gibbs Free Energy ($\Delta G$)

A thermodynamic state function defined as $\Delta G = \Delta H - T\Delta S$, serving as the criterion for spontaneity at constant temperature and pressure: spontaneous/exergonic if $\Delta G < 0$, non-spontaneous/endergonic if $\Delta G > 0$, and at equilibrium if $\Delta G = 0$.

Arrhenius Equation

A mathematical formula ($k = A e^{-\frac{E_a}{RT}}$) that models the temperature dependence of chemical reaction rate constants, linking the rate constant $k$ to the activation energy $E_a$, absolute temperature $T$, and pre-exponential frequency factor $A$.

Henderson-Hasselbalch Equation

An equation used to calculate the pH of a buffer solution: $pH = pK_a + \log\left(\frac{[\text{A}^-]}{[\text{HA}]}\right)$, relating the solution pH to the acid dissociation constant $pK_a$ and the ratio of conjugate base to weak acid concentrations.

Nernst Equation

An electrochemical relationship calculating the reduction potential of an electrochemical half-cell or full cell as a function of the standard potential, temperature, number of electrons transferred, and the reaction quotient ($E = E^\circ - \frac{RT}{nF}\ln(Q)$).

Fenton Reaction

An inorganic oxidation-reduction reaction wherein ferrous iron ($\text{Fe}^{2+}$) reduces hydrogen peroxide ($\text{H}_2\text{O}_2$) to produce the highly reactive and damaging hydroxyl radical ($\cdot\text{OH}$).

Hückel's Rule

A rule of organic chemistry specifying that a planar, monocyclic ring with continuous p-orbital overlap exhibits aromatic stability if it possesses exactly $(4n + 2)$ delocalized $\pi$-electrons, where $n$ is a non-negative integer.

Keto-Enol Tautomerism

A chemical equilibrium between a ketone or aldehyde constitutional isomer and an enol isomer via the intramolecular migration of a proton and repositioning of a double bond.

Isoelectric Point ($pI$)

The specific pH at which an amino acid, peptide, or protein carries no net electrical charge and exists predominantly in its dipolar zwitterionic form.

Glutathione

A biological tripeptide (composed of glutamate, cysteine, and glycine) that acts as a vital non-enzymatic cellular antioxidant by using its free thiol ($-\text{SH}$) group to neutralize reactive oxygen species and free radicals.