MCAT flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Ideal gas law

PV = nRT relates pressure, volume, moles, and absolute temperature. At constant temperature, pressure and volume are inversely proportional; at constant pressure, volume is directly proportional to temperature.

Henderson–Hasselbalch equation

pH = pKa + log([conjugate base]/[weak acid]). A buffer resists pH change best within about one pH unit of its pKa, and pH equals pKa when the acid and base forms are equal.

Michaelis–Menten kinetics

v = Vmax[S]/(Km + [S]). Km is the substrate concentration at half of Vmax; a smaller Km indicates tighter enzyme–substrate binding, while Vmax reflects enzyme amount and turnover.

Gibbs free energy relationship

ΔG = ΔH − TΔS. A negative ΔG indicates a spontaneous process; ΔG° = −RT ln Keq, so an equilibrium constant greater than one corresponds to a negative standard free energy change.

Le Chatelier's principle

A system at equilibrium shifts to counteract an applied stress. Adding reactant shifts toward products; raising pressure favors the side with fewer gas moles; heating favors the endothermic direction.

SN1 versus SN2 mechanisms

SN2 is a single concerted step with backside attack and inversion, favored by methyl or primary substrates and strong nucleophiles. SN1 proceeds through a carbocation and is favored by tertiary substrates and polar protic solvents.

Mendelian dihybrid ratio

Crossing two heterozygotes for unlinked genes yields a 9:3:3:1 phenotypic ratio when complete dominance applies. A monohybrid cross yields a 3:1 phenotype and 1:2:1 genotype ratio.

Resting membrane potential

The neuron's resting potential near −70 mV arises mainly from potassium leak permeability and the sodium-potassium pump. Depolarization opens voltage-gated sodium channels; repolarization follows potassium efflux.

Osmosis and tonicity

Water moves across a semipermeable membrane toward higher solute concentration. A cell in hypertonic solution shrinks, in hypotonic solution swells, and in isotonic solution maintains steady volume.

Hormone signaling pathways

Peptide hormones bind surface receptors and act through second messengers such as cAMP, acting rapidly. Steroid hormones cross membranes, bind intracellular receptors, and alter transcription, producing slower, longer-lasting effects.

Hardy–Weinberg equilibrium

Allele frequencies p + q = 1 and genotype frequencies p² + 2pq + q² = 1 hold in the absence of selection, mutation, migration, drift, and nonrandom mating. Deviations suggest evolution is occurring.

Classical conditioning

A neutral conditioned stimulus repeatedly paired with an unconditioned stimulus comes to elicit a conditioned response. Extinction weakens the response, but spontaneous recovery can reveal the association persists.

Operant conditioning

Reinforcement increases and punishment decreases behavior frequency. Positive means adding a stimulus, negative means removing one; variable-ratio schedules produce high, persistent response rates.

Piaget's cognitive stages

Development proceeds through sensorimotor, preoperational, concrete operational, and formal operational stages. Object permanence emerges in infancy; conservation appears in concrete operational thought around age seven.

Erikson's psychosocial crises

Each life stage poses a crisis whose resolution yields a virtue, such as trust versus mistrust in infancy, industry versus inferiority in school age, and identity versus role confusion in adolescence.

Weber's ideal bureaucracy

Weber described bureaucracy as characterized by division of labor, hierarchical authority, written rules, impersonal treatment of clients, and hiring based on merit rather than personal ties.

Durkheim's suicide typology

Egoistic suicide reflects insufficient social integration; altruistic reflects excessive integration; anomic follows normlessness or sudden change; fatalistic follows excessive regulation of individuals' lives.

Fundamental attribution error

Observers tend to overestimate dispositional causes and underestimate situational causes when explaining others' behavior, while attributing their own behavior more heavily to circumstances.

Self-serving bias

People attribute their successes to internal qualities such as ability and effort, but attribute failures to external factors such as bad luck or task difficulty, protecting self-esteem.

Cognitive dissonance

Holding inconsistent cognitions produces discomfort that motivates change. Festinger's classic study showed underpaid participants rated a dull task as more enjoyable, reducing dissonance by changing attitudes.

Demographic transition model

Populations move from high birth and death rates through a growth phase of falling death rates, then declining birth rates, toward low stable rates in industrialized societies.

Social stratification

Societies rank groups by unequal access to resources, power, and prestige. Class, status, and party are Weber's dimensions; caste is closed, while class allows some mobility.

Confirmation bias

The tendency to seek, interpret, and remember information that supports existing beliefs while discounting contradictory evidence, which can distort hypothesis testing and diagnosis.

Internal versus external validity

Internal validity is confidence that the independent variable caused the outcome; external validity is generalizability beyond the study sample and setting. Random assignment strengthens internal validity.

Sensitivity and specificity

Sensitivity is the true-positive rate among people with disease; specificity is the true-negative rate among people without disease. Positive predictive value also depends on disease prevalence.

Standard error of the mean

The standard error equals the sample standard deviation divided by the square root of sample size. It estimates variability of sample means and shrinks as sample size grows.

Statistical significance

A p-value is the probability of obtaining data at least as extreme as observed, assuming the null hypothesis is true. It is not the probability that the null hypothesis is correct.

Correlation versus causation

An observed association does not prove that one variable causes another. Reverse causation, confounding variables, and selection effects can all produce correlation without a causal relationship.

Deductive versus inductive reasoning

Deduction derives specific conclusions from general premises and is judged valid or invalid. Induction generalizes from specific observations and is judged strong or weak, never fully certain.

Control group purpose

A control group receives no treatment or a placebo, providing a baseline against which treatment effects are compared and helping isolate the independent variable's effect.

Blinding in experiments

Single-blind designs conceal treatment from participants; double-blind designs also conceal it from researchers. Blinding reduces demand characteristics and experimenter expectancy effects that bias results.

Effect size versus p-value

Effect size quantifies the magnitude of a difference or association, such as Cohen's d. A very small p-value can accompany a trivial effect when sample size is large.