USJ Medical Sciences Concours - Medicine, Dental Medicine & Pharmacy cheat sheet

Membrane transport: simple diffusion follows the concentration gradient without ATP; facilitated diffusion uses channels or carriers; primary active transport (e.g., Na+/K+ ATPase) hydrolyzes ATP; secondary active transport couples to an ion gradient.

Organelle functions: nucleus stores DNA; rough ER synthesizes secretory proteins; smooth ER handles lipid synthesis and detoxification; Golgi modifies and sorts proteins; lysosomes degrade material; mitochondria perform oxidative phosphorylation.

Central dogma: DNA is replicated semiconservatively; transcription produces mRNA; translation at ribosomes uses codons (three bases) to specify amino acids; the genetic code is redundant and nearly universal.

Mendelian genetics: a monohybrid heterozygote cross gives a 3:1 phenotype ratio and a 1:2:1 genotype ratio; a dihybrid heterozygote cross gives 9:3:3:1 when genes assort independently.

Resting membrane potential is about −70 mV in neurons, maintained by K+ leak channels and the Na+/K+ ATPase; depolarization opens voltage-gated Na+ channels, and repolarization depends on K+ efflux.

Cardiac output = heart rate × stroke volume; mean arterial pressure ≈ cardiac output × total peripheral resistance; blood flow is driven by pressure gradients.

Homeostasis uses negative feedback: a sensor detects deviation, an integrating center compares it to a set point, and an effector produces a response that opposes the deviation; positive feedback amplifies a change (e.g., labor contractions).

Renal physiology: glomerular filtration occurs in Bowman's capsule; the proximal tubule reabsorbs most filtered water and solutes; the loop of Henle creates a medullary osmotic gradient; ADH increases collecting duct water permeability.

Gas exchange: alveolar partial pressure of oxygen (~100 mmHg) exceeds venous (~40 mmHg), so O2 diffuses into blood; CO2 diffuses out because venous PCO2 (~45 mmHg) exceeds alveolar (~40 mmHg).

Mole: n = m/M; one mole = 6.022×10^23 particles; at STP (0 °C, 1 atm) one mole of ideal gas occupies 22.4 L.

Ideal gas law: PV = nRT, with R = 0.08206 L·atm·mol−1·K−1 or 8.314 J·mol−1·K−1; temperature must be in kelvin.

Acids and bases: pH = −log[H+]; pOH = −log[OH−]; pH + pOH = 14 at 25 °C; strong acids dissociate completely, weak acids partially (Ka).

Buffers resist pH change; Henderson–Hasselbalch: pH = pKa + log([A−]/[HA]); buffering is most effective when pH is within about one unit of pKa.

Le Chatelier's principle: adding reactant shifts equilibrium toward products; increasing pressure favors the side with fewer gas moles; increasing temperature favors the endothermic direction.

Organic functional groups: alcohols (–OH), aldehydes (–CHO), ketones (C=O), carboxylic acids (–COOH), amines (–NH2), esters (–COO–); the oxidation state of carbon rises with more C–O bonds.

Enzyme kinetics: Michaelis–Menten v = Vmax[S]/(Km + [S]); Km = [S] at Vmax/2; competitive inhibitors raise apparent Km, noncompetitive inhibitors lower Vmax.

Thermodynamics: ΔG = ΔH − TΔS; ΔG < 0 spontaneous; ΔG° = −RT ln K; coupled reactions use a favorable ΔG to drive an unfavorable one.

Kinematics: v = v0 + at; x = x0 + v0t + ½at²; v² = v0² + 2a(x − x0) for constant acceleration.

Newton's laws: ΣF = ma; action–reaction pairs act on different bodies; friction f ≤ μN; weight = mg.

Work–energy: W = Fd cosθ; kinetic energy KE = ½mv²; gravitational potential energy PE = mgh; conservation applies when only conservative forces do work.

Fluids: pressure P = F/A; hydrostatic pressure P = P0 + ρgh; buoyant force equals the weight of displaced fluid (Archimedes).

Continuity equation: A1v1 = A2v2 for incompressible flow; Bernoulli's equation P + ½ρv² + ρgh = constant along a streamline.

Poiseuille's law: Q = πΔPr⁴/(8ηL); doubling radius increases flow 16-fold; resistance is inversely proportional to r⁴.

Electricity: V = IR; power P = IV = I²R = V²/R; resistors in series add, in parallel reciprocals add: 1/Rp = Σ1/Ri.

Waves: v = fλ; sound intensity level β = 10 log(I/I0) dB; the Doppler shift depends on relative motion between source and observer.

Optics: thin lens 1/f = 1/do + 1/di; magnification m = −di/do; converging lenses have positive f; total internal reflection occurs when incidence exceeds the critical angle.

Quadratic formula: ax² + bx + c = 0 gives x = [−b ± √(b² − 4ac)]/(2a); the discriminant b² − 4ac determines real, repeated, or complex roots.

Logarithms: log(ab) = log a + log b; log(a/b) = log a − log b; log(a^n) = n log a; ln e = 1; pH and decibel scales are logarithmic.

Exponential growth/decay: N(t) = N0 e^{kt}; k > 0 growth, k < 0 decay; half-life t½ = ln2/|k|.

Probability: P(A∪B) = P(A) + P(B) − P(A∩B); independent events P(A∩B) = P(A)P(B); complement P(A′) = 1 − P(A).

Conditional probability and Bayes: P(A|B) = P(A∩B)/P(B); P(A|B) = P(B|A)P(A)/P(B).

Binomial: P(X = k) = C(n,k) p^k (1−p)^{n−k}; mean np; variance np(1−p).

Descriptive statistics: mean is sensitive to outliers; median is the middle value; standard deviation measures spread; z = (x − μ)/σ.

Diagnostic tests: sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); positive predictive value depends on prevalence.

Controlled experiment: an independent variable is manipulated, a dependent variable is measured, and other variables are held constant; a control group receives no treatment or a placebo.

Validity versus reliability: validity means measuring the intended construct; reliability means consistent repeated results; precise instruments improve reliability, not necessarily validity.

Randomization reduces selection bias; blinding reduces observer and participant bias; a placebo controls for expectation effects.

Correlation does not establish causation; causal inference is strengthened by temporal order, dose–response, biological plausibility, and randomized controlled trials.

Significant figures: multiplication/division keep the least number of significant figures; addition/subtraction keep the least number of decimal places.

Unit conversion: multiply by ratios equal to one and cancel units; check that both sides of an equation have identical dimensions.

Error propagation: for addition/subtraction absolute uncertainties add; for multiplication/division relative uncertainties add; percentage error = |measured − accepted|/accepted × 100%.

Study designs: cross-sectional measures exposure and outcome at one time; cohort follows exposed and unexposed groups forward; case–control compares diseased and non-diseased retrospectively.

Main idea: the central claim supported by most paragraphs; details, examples, and dates usually support rather than state it.

Explicit versus implied: an explicit statement is directly written; an inference is logically derived from textual evidence and must not exceed what the passage supports.

Reference words: pronouns (it, they, this, these) refer to the nearest compatible noun phrase; check number and logical fit.

Signpost words: because, therefore, thus, consequently signal cause or result; however, although, whereas signal contrast; moreover, furthermore signal addition.

Hedging: may, might, suggest, appear, likely indicate uncertainty; absolute words such as always, never, proves often signal overstatement.

Scientific vocabulary in context: use surrounding definitions, examples, or contrasts to infer meaning; do not rely on everyday meanings when a technical sense is intended.

Data interpretation: read axis labels and units first; distinguish absolute changes from percentage changes; a steeper slope indicates a faster rate.