Lebanese University Faculty of Public Health Entrance Exam cheat sheet

Cell theory: all organisms are composed of one or more cells; the cell is the basic unit of life; all cells arise from pre-existing cells.

Prokaryotes lack a membrane-bound nucleus and membrane-bound organelles; their ribosomes are 70S (50S + 30S subunits). Eukaryotic cytoplasmic ribosomes are 80S (60S + 40S).

DNA replication is semiconservative. In PCR, denaturation (~95 °C) separates strands, annealing (~50–65 °C) binds primers, extension (~72 °C) uses Taq polymerase.

Transcription: RNA polymerase reads the template strand 3′→5′ and synthesizes RNA 5′→3′. In eukaryotes, introns are spliced out before translation.

Mendelian ratios: monohybrid F2 = 3:1 phenotype, 1:2:1 genotype; dihybrid F2 = 9:3:3:1 for independently assorting unlinked genes.

Hardy–Weinberg equilibrium requires no mutation, no migration, random mating, infinite population size, and no selection; then p² + 2pq + q² = 1 and p + q = 1.

Aerobic respiration net ATP yield is commonly taught as ~30–32 ATP per glucose (glycolysis 2, Krebs cycle 2, oxidative phosphorylation ~26–28). Anaerobic glycolysis yields 2 ATP per glucose.

Blood groups: ABO alleles IA and IB are codominant; i is recessive. Rh-positive (D antigen present) is dominant over Rh-negative.

Photosynthesis: light reactions in thylakoid membranes produce ATP and NADPH; the Calvin cycle in the stroma fixes CO2 using RuBisCO.

Mole: n = m/M; 1 mol contains 6.022×10²³ particles. Molarity M = moles solute / liters solution. At STP (0 °C, 1 atm), 1 mol 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.

pH = −log[H⁺]; pOH = −log[OH⁻]; pH + pOH = 14 at 25 °C. Strong acid/base fully dissociates; weak acid uses Ka and ICE table.

Henderson–Hasselbalch: pH = pKa + log([A⁻]/[HA]). A buffer is most effective when pH is within ±1 of pKa.

Le Chatelier: adding reactant shifts equilibrium toward products; increasing pressure shifts toward the side with fewer gas moles; a catalyst changes rate but not equilibrium position.

Oxidation is loss of electrons (increase in oxidation number); reduction is gain of electrons. In a galvanic cell, oxidation occurs at the anode and reduction at the cathode.

Bond polarity follows electronegativity difference: <0.4 nonpolar covalent, 0.4–1.7 polar covalent, >1.7 ionic (Pauling scale, approximate).

First law of thermodynamics: ΔU = q + w. Enthalpy change ΔH < 0 indicates exothermic; ΔG = ΔH − TΔS < 0 indicates a spontaneous process at constant T and P.

Kinematics: v = v₀ + at; x = v₀t + ½at²; v² = v₀² + 2ax (constant acceleration only).

Newton's second law: ΣF = ma. Weight W = mg with g ≈ 9.8 m/s² near Earth's surface. Friction f = μN.

Work W = Fd cosθ; kinetic energy KE = ½mv²; gravitational potential energy near Earth PE = mgh; power P = W/t.

Conservation of mechanical energy: ½mv₁² + mgh₁ = ½mv₂² + mgh₂ when only conservative forces act.

Ohm's law V = IR; electric power P = VI = I²R = V²/R. Resistors in series add; in parallel 1/R_eq = Σ1/Rᵢ.

Wave equation v = fλ. For a string fixed at both ends, fundamental frequency f₁ = v/(2L).

Snell's law n₁ sinθ₁ = n₂ sinθ₂; refractive index n = c/v. Total internal reflection occurs when the angle exceeds the critical angle θc = sin⁻¹(n₂/n₁).

Half-life: after n half-lives, remaining fraction = (1/2)ⁿ. Activity A = λN, with λ = ln2 / t½.

Quadratic formula: x = [−b ± √(b² − 4ac)] / (2a). Discriminant b² − 4ac > 0 gives two real roots, = 0 one repeated root, < 0 complex roots.

Logarithm rules: log(ab) = log a + log b; log(a/b) = log a − log b; log(aⁿ) = n log a; log_b x = ln x / ln b.

Derivative rules: d/dx xⁿ = nxⁿ⁻¹; d/dx eˣ = eˣ; d/dx ln x = 1/x; product rule (uv)′ = u′v + uv′; chain rule d/dx f(g(x)) = f′(g(x))·g′(x).

Integral: ∫xⁿ dx = xⁿ⁺¹/(n+1) + C for n ≠ −1; ∫(1/x) dx = ln|x| + C. The definite integral equals the signed area under the curve.

Trigonometric identity: sin²θ + cos²θ = 1. Law of cosines: c² = a² + b² − 2ab cos C.

Probability: P(A or B) = P(A) + P(B) − P(A and B); P(A and B) = P(A)·P(B|A). Independent events satisfy P(A and B) = P(A)·P(B).

Mean of a data set = Σxᵢ/n; sample variance s² = Σ(xᵢ − x̄)²/(n − 1); standard deviation is the square root of variance.

Arithmetic sequence: aₙ = a₁ + (n − 1)d; sum Sₙ = n(a₁ + aₙ)/2. Geometric sequence: aₙ = a₁rⁿ⁻¹; sum Sₙ = a₁(1 − rⁿ)/(1 − r) for r ≠ 1.

WHO defines health as a state of complete physical, mental, and social well-being, not merely the absence of disease or infirmity (1948 Constitution).

Levels of prevention: primary (prevent onset, e.g., vaccination), secondary (early detection, e.g., screening), tertiary (limit disability and rehabilitate).

Incidence counts new cases in a population over a period; prevalence counts all existing cases at a point or period. Prevalence ≈ incidence × average duration.

Crude mortality rate = (deaths in a year / mid-year population) × 1,000. Infant mortality rate = (deaths under age 1 / live births) × 1,000.

Herd immunity threshold ≈ 1 − 1/R₀; for measles R₀ ≈ 12–18, requiring roughly 92–95% coverage.

Epidemiologic triad: agent, host, and environment. A vector is an organism that transmits a pathogen, such as Anopheles mosquitoes for malaria.

Noncommunicable diseases (cardiovascular disease, cancer, diabetes, chronic respiratory disease) account for roughly 70% of global deaths according to WHO estimates.

Hand hygiene, safe water, sanitation, and food safety are core environmental health measures for interrupting fecal–oral transmission.

Lebanon's public health system includes the Ministry of Public Health, primary health care centers, and the National Social Security Fund; the country has faced cholera and measles outbreaks in recent years.

A hypothesis must be testable and falsifiable; a prediction states an observable outcome if the hypothesis is true.

Independent variable is manipulated; dependent variable is measured; controlled variables are held constant to reduce confounding.

A controlled experiment compares a treatment group with a control group that differs only in the variable under study; randomization reduces selection bias.

Correlation does not imply causation; confounding variables and reverse causation can produce spurious associations.

Sensitivity = true positives / (true positives + false negatives); specificity = true negatives / (true negatives + false positives).

Positive predictive value depends on prevalence: PPV = TP / (TP + FP). A test can have high sensitivity and low PPV in a low-prevalence population.

In a graph, read the axes and units first; slope = Δy/Δx; a steeper slope means a greater rate of change.

Statistically significant usually means p < 0.05, indicating the observed result is unlikely under the null hypothesis; significance does not measure effect size.

Subject–verb agreement: a singular subject takes a singular verb; compound subjects joined by 'and' take a plural verb unless they form a single idea.

Active voice: subject performs the action (The nurse administered the vaccine). Passive voice: subject receives the action (The vaccine was administered by the nurse).

Punctuation: a comma splice joins two independent clauses with only a comma; use a semicolon, a period, or a coordinating conjunction.

Apostrophes show possession (the patient's chart) or contraction (it's = it is); 'its' is possessive without an apostrophe.

In scientific writing, prefer precise, concise, and objective language; avoid vague qualifiers such as 'very' or 'a lot' when a number is available.

A paragraph should develop one central idea, usually stated in a topic sentence, followed by supporting evidence and a concluding or transitional sentence.

Formal communication in health settings uses respectful, plain language, avoids jargon with patients, and confirms understanding through teach-back.

Reading comprehension strategy: identify the main claim, distinguish evidence from opinion, and note the author's purpose (inform, persuade, explain).