Lebanese University Faculty of Public Health Entrance Exam key terms

The set of automatic adjustments that keep conditions inside an organism stable, such as body temperature, blood glucose, and water balance, despite changes in the surrounding environment.

A control loop in which a rise in a measured value triggers a response that lowers it back toward a set point, as when high blood glucose stimulates insulin release.

The net movement of water across a partially permeable membrane from a region of higher water concentration to one of lower water concentration, driven by differences in solute concentration.

The spontaneous spreading of particles from regions of higher concentration to regions of lower concentration, caused by random molecular motion and requiring no energy input from the cell.

A protein that speeds up a specific biochemical reaction by lowering its activation energy, binding its substrate at an active site whose shape determines which reactions it can catalyse.

Loss of a protein's functional three-dimensional shape caused by heat, extreme pH, or chemicals, which disrupts bonds holding the structure and usually destroys enzyme activity irreversibly.

Cell division that produces two genetically identical daughter cells with the same chromosome number as the parent, used for growth, repair, and replacement of body tissues.

Two successive divisions that produce four daughter cells each with half the chromosome number of the parent, generating genetic variation through crossing over and independent assortment.

A thread-like structure of DNA wrapped around proteins that carries genes; human body cells contain 46 chromosomes arranged in 23 pairs, while gametes contain 23 single chromosomes.

The ability of bacteria to survive and multiply in the presence of a drug that would normally kill or inhibit them, arising through mutation or gene transfer and spread by selective pressure from misuse.

The process by which individuals with inherited traits that improve survival or reproduction leave more offspring, so those traits become more common in later generations of a population.

The amount of substance containing 6.022 × 10^23 elementary entities, allowing chemists to convert between mass in grams and number of particles using molar mass.

A concentration unit equal to the number of moles of solute dissolved in one litre of solution, commonly written M and used to prepare laboratory solutions and calculate dilutions.

A logarithmic scale from 0 to 14 expressing the acidity of a solution as the negative logarithm of hydrogen ion concentration, with 7 neutral and lower values more acidic.

A solution of a weak acid with its conjugate base, or a weak base with its conjugate acid, that resists large changes in pH when small amounts of acid or alkali are added.

A procedure in which a solution of known concentration is added gradually to a measured volume of unknown concentration until the reaction reaches its end point, allowing the unknown to be calculated.

The calculation of quantities of reactants and products in a balanced chemical equation, using molar ratios to predict masses, volumes, or moles consumed and formed.

A chemical change in which an atom, ion, or molecule loses electrons, shown as an increase in oxidation number; it is always accompanied by a matching reduction.

A bond formed when two atoms share one or more pairs of electrons, typically between non-metals, producing discrete molecules or extended networks rather than lattices of ions.

Attractions between separate molecules, including hydrogen bonding, dipole interactions, and weak dispersion forces, which explain boiling points, solubility, and the physical behaviour of substances.

The relationship stating that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass, written as F = ma.

Motion of an object under gravity alone, with air resistance ignored, so that it accelerates downward at about 9.8 metres per second squared near the Earth's surface regardless of mass.

Work is the transfer of energy when a force moves an object through a distance; energy is the capacity to do work and is conserved, changing only between forms such as kinetic and potential.

For a conductor at constant temperature, the current through it is directly proportional to the potential difference across it, giving the relation V = IR with resistance R in ohms.

The time required for half of the radioactive nuclei in a sample to decay, a constant for each isotope that is unaffected by temperature, pressure, or chemical state.

An increase in which a quantity grows at a rate proportional to its current size, producing a curve that rises ever more steeply and doubling in equal time intervals.

The instantaneous rate at which one quantity changes with respect to another, interpreted graphically as the slope of the tangent to a curve at a given point.

The accumulated total of a quantity over an interval, interpreted graphically as the area under a curve between two limits and computed as the reverse of differentiation.

A number between 0 and 1 expressing how likely an event is, calculated for equally likely outcomes as the count of favourable outcomes divided by the count of all possible outcomes.

Sensitivity is the proportion of truly diseased people a test correctly identifies as positive; specificity is the proportion of truly healthy people it correctly identifies as negative.

The probability that a person with a positive test result actually has the disease, which depends on test accuracy and on how common the disease is in the tested population.

Incidence counts new cases arising in a population over a period; prevalence counts all existing cases at one moment, so a longer-lasting disease raises prevalence even when incidence is unchanged.

Indirect protection of unvaccinated people that arises when a sufficiently large share of a population is immune, interrupting chains of transmission and limiting outbreaks.

An unmeasured factor linked both to the supposed cause and to the outcome, which can create or hide an apparent association and must be controlled by design or analysis.

An experiment in which participants are allocated by chance to treatment or control groups, so that known and unknown confounders are balanced and causal effects can be estimated fairly.

Correlation means two variables change together; causation means one produces the other. Correlation alone cannot establish causation because confounders, chance, or reverse direction may explain the link.

Independent scrutiny of a research report by experts in the same field before publication, intended to check methods, analysis, and claims, though it does not guarantee that findings are correct.

A result is statistically significant when the observed effect is unlikely to have arisen by chance alone, conventionally when the probability of such a result under the null hypothesis is below 0.05.

A conclusion drawn from evidence rather than stated directly, such as identifying an author's implied attitude or the assumption a passage depends on but never spells out.

The central claim a passage develops and supports throughout, distinguishable from supporting details because every other sentence serves to explain, illustrate, or defend it.