MCAT CONCEPTS & REASONING
Use this free library to review a concept, follow a worked example, and test the same idea under changed conditions. The catalog spans 241 lessons across the four MCAT sections plus research and data reasoning. Browse other free tools.
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BIOLOGY & BIOCHEMISTRY
Biology & Biochemistry
Build from molecules and cells to metabolism, genetics, physiology, and integrated biological systems.
69 lessons
CHEMISTRY & PHYSICS
Chemistry & Physics
Use quantitative models and molecular reasoning across chemistry, physics, laboratory methods, and organic reactions.
67 lessons
PSYCHOLOGY & SOCIOLOGY
Psychology & Sociology
Connect behavior, cognition, social interaction, institutions, demographics, and inequality to evidence.
71 lessons
RESEARCH & DATA
Research & Data
Move from study design and measurement to graphs, uncertainty, statistics, and multi-figure evidence.
17 lessons
CARS
CARS
Practice comprehension, argument structure, inference, transfer, new evidence, and original passage walkthroughs.
17 lessons
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Showing all 241 lessons. Without JavaScript, open the section lists below or use your browser’s Find command.
Biology & Biochemistry — 69 lessons
- Amino acid and peptide charge: count the groups that can change — Proteins and enzymes
- Enzyme kinetics: read the curve before naming the inhibitor — Proteins and enzymes
- How amino acid properties shape a peptide — Proteins and enzymes
- Protein folding, stability, and denaturation — Proteins and enzymes
- Choosing and interpreting protein purification methods — Proteins and enzymes
- How enzymes catalyze reactions and regulate pathways — Proteins and enzymes
- Protein binding and cooperativity — Proteins and enzymes
- Nucleotides, base pairing, and DNA stability — DNA and gene expression
- DNA replication, proofreading, and repair — DNA and gene expression
- Transcription and RNA processing — DNA and gene expression
- Translation and the genetic code — DNA and gene expression
- Mendelian inheritance and genetic probability — Inheritance and evolution
- Meiosis and genetic recombination — Inheritance and evolution
- Biological energy, ATP, and coupled reactions — Metabolism and energy
- Carbohydrate structures and glycosidic bonds — Metabolism and energy
- Glycolysis and fermentation — Metabolism and energy
- Lipids and membrane properties — Cells and membranes
- Membrane transport and osmosis — Cells and membranes
- Organelles and protein trafficking — Cells and membranes
- Prokaryotic cells and growth — Microbes and viruses
- Cell-cycle checkpoints and cancer — Cell division and development
- Neuron structure and signal flow — Nervous and endocrine control
- Resting membrane potential — Nervous and endocrine control
- Action potentials and conduction — Nervous and endocrine control
- Synaptic transmission and summation — Nervous and endocrine control
- Nervous-system organization and reflex pathways — Nervous and endocrine control
- Autonomic control of organs — Nervous and endocrine control
- Hormone signals and cellular receptors — Nervous and endocrine control
- Endocrine feedback and hormone axes — Nervous and endocrine control
- Breathing mechanics and alveolar gas exchange — Organ systems and homeostasis
- The cardiac cycle and circulation — Organ systems and homeostasis
- Chromatin and eukaryotic gene regulation — DNA and gene expression
- Bacterial operons and gene regulation — DNA and gene expression
- Cloning and recombinant DNA — DNA and gene expression
- Reading PCR, sequencing, and DNA blot results — DNA and gene expression
- Pedigrees and inheritance beyond a simple dominant model — Inheritance and evolution
- Genetic linkage and mapping — Inheritance and evolution
- Mutations and their functional consequences — Inheritance and evolution
- Population genetics and Hardy–Weinberg reasoning — Inheritance and evolution
- Evolution, selection, and speciation — Inheritance and evolution
- Making and storing glucose — Metabolism and energy
- The pentose phosphate pathway and reducing power — Metabolism and energy
- Pyruvate oxidation and the citric acid cycle — Metabolism and energy
- Electron transport and ATP synthesis — Metabolism and energy
- Fatty acid metabolism and ketone bodies — Metabolism and energy
- Amino acid metabolism and nitrogen handling — Metabolism and energy
- The cytoskeleton and cell movement — Cells and membranes
- Cell junctions and tissue organization — Cells and membranes
- Bacterial gene transfer and antibiotic resistance — Microbes and viruses
- Viral structure and replication — Microbes and viruses
- Gametogenesis and fertilization — Cell division and development
- Early embryonic development — Cell division and development
- Blood-gas transport and pH control — Organ systems and homeostasis
- Capillary exchange and lymph flow — Organ systems and homeostasis
- Blood cells and clotting — Organ systems and homeostasis
- Innate and adaptive immunity — Organ systems and homeostasis
- Antibodies and antigen presentation — Organ systems and homeostasis
- Digestion and nutrient absorption — Organ systems and homeostasis
- Kidney filtration and solute handling — Organ systems and homeostasis
- Urine concentration and water balance — Organ systems and homeostasis
- Reproductive hormone cycles — Organ systems and homeostasis
- Pregnancy, birth, and lactation — Organ systems and homeostasis
- Muscle contraction and calcium — Organ systems and homeostasis
- Muscle types, force, and energy use — Organ systems and homeostasis
- Bone, joints, and calcium balance — Organ systems and homeostasis
- Skin and temperature regulation — Organ systems and homeostasis
- Measuring gene expression and testing gene function — DNA and gene expression
- Fuel use in fed, fasting, and exercise states — Metabolism and energy
- Cell fate, stem cells, and differentiation — Cell division and development
Chemistry & Physics — 67 lessons
- Moles, formulas, and yield: conserve the reacting material — Atoms and chemical quantities
- Aqueous ions and concentration: keep amount and volume separate — Aqueous solutions and acid–base chemistry
- Acid–base strength: distinguish concentration from dissociation — Aqueous solutions and acid–base chemistry
- Weak acids, bases, and salts: choose a defensible pH calculation — Aqueous solutions and acid–base chemistry
- Buffers: explain pH resistance and its limits — Aqueous solutions and acid–base chemistry
- Motion: translate between vectors, units, and graphs — Motion and mechanical energy
- Net force and friction: build the right free-body diagram — Motion and mechanical energy
- Work, energy, and power: choose the useful conservation model — Motion and mechanical energy
- Waves: separate amplitude, frequency, and propagation speed — Waves, sound, and light
- Pressure, buoyancy, and the role of fluid interfaces — Fluids and gases
- Ideal fluid flow: use continuity before Bernoulli — Fluids and gases
- Ideal gases: keep the controlled variables visible — Fluids and gases
- Electric fields and potential: separate force from energy — Electricity and electrochemistry
- Resistor circuits: track current, voltage, and measurement — Electricity and electrochemistry
- Sound intensity: reason with attenuation and a logarithmic scale — Waves, sound, and light
- Electromagnetic light: connect wavelength, photons, and polarization — Waves, sound, and light
- Refraction and reflection: follow light across an interface — Waves, sound, and light
- Atomic identity and nuclear change: conserve charge and nucleon count — Atoms and chemical quantities
- Electron configurations: account for orbitals and unpaired electrons — Atoms and chemical quantities
- Periodic trends: explain a comparison from electron structure — Atoms and chemical quantities
- Redox bookkeeping: balance atoms, charge, and electrons — Electricity and electrochemistry
- Galvanic cells: connect half-reactions to cell potential — Electricity and electrochemistry
- Lewis structures: use formal charge and resonance together — Molecular structure and analytical evidence
- Molecular geometry: connect bonding, shape, and polarity — Molecular structure and analytical evidence
- Stereochemistry: distinguish connectivity, configuration, and identity — Molecular structure and analytical evidence
- Intermolecular forces: predict physical properties from structure — Molecular structure and analytical evidence
- Extraction: use partitioning and pH to separate a mixture — Separation and measurement
- Chromatography: connect retention to the two phases — Separation and measurement
- Functional groups: follow the bonds that change in a reaction — Organic reaction reasoning
- Infrared spectra: use functional-group evidence cautiously — Molecular structure and analytical evidence
- Heat and temperature: interpret a calorimetry measurement — Thermodynamics and reaction rates
- Reaction enthalpy: combine Hess cycles and bond-energy estimates — Thermodynamics and reaction rates
- Entropy and temperature: explain when a process is favored — Thermodynamics and reaction rates
- Free energy and equilibrium: distinguish standard from actual conditions — Thermodynamics and reaction rates
- Rate laws: infer reaction order and test a proposed mechanism — Thermodynamics and reaction rates
- Torque and levers: solve a static-equilibrium problem — Motion and mechanical energy
- Viscous flow: explain pressure loss and radius dependence — Fluids and gases
- Gas mixtures: calculate partial pressure from composition — Fluids and gases
- Capacitors: distinguish stored charge, voltage, and energy — Electricity and electrochemistry
- Magnetic forces: predict a charged particle’s deflection — Electricity and electrochemistry
- Electrolysis: use charge to predict product yield — Electricity and electrochemistry
- Resonance: predict allowed patterns in strings and air columns — Waves, sound, and light
- Doppler shifts and ultrasound: infer motion from reflected waves — Waves, sound, and light
- Interference and diffraction: read a pattern as wave evidence — Waves, sound, and light
- Lenses and mirrors: predict image location, size, and orientation — Waves, sound, and light
- UV–visible absorption: connect color, conjugation, and concentration — Molecular structure and analytical evidence
- Proton NMR: combine equivalence and splitting as structural evidence — Molecular structure and analytical evidence
- Radioactive decay: read half-life from linear and semilog data — Atoms and chemical quantities
- Atomic spectra and the photoelectric effect: test quantized energy — Atoms and chemical quantities
- Mass spectra: distinguish mass-to-charge, isotopes, and fragments — Molecular structure and analytical evidence
- Titration curves: distinguish endpoint, equivalence, and buffering — Aqueous solutions and acid–base chemistry
- Conformation: tell permitted rotation from a change in configuration — Molecular structure and analytical evidence
- Chiral mixtures: interpret optical rotation and plan a separation — Separation and measurement
- Alcohol substitution: reason about leaving groups and competing pathways — Organic reaction reasoning
- Carbonyl addition: predict products and reversible protection — Organic reaction reasoning
- Organic redox: track oxidation state through functional-group changes — Organic reaction reasoning
- Acyl substitution: explain reactivity, hydrolysis, and bond exchange — Organic reaction reasoning
- Alpha-amino-acid synthesis: track atoms and stereochemical limits — Organic reaction reasoning
- Aromatic heterocycles: decide which electron pairs can react — Organic reaction reasoning
- The first law: account for heat, work, and internal energy — Thermodynamics and reaction rates
- Phase changes: read heating curves and pressure–temperature diagrams — Thermodynamics and reaction rates
- Distillation: infer separation from volatility and a temperature record — Separation and measurement
- Equilibrium shifts: separate the reaction quotient from the constant — Thermodynamics and reaction rates
- Solubility: use common ions, pH, and complex formation — Aqueous solutions and acid–base chemistry
- Activation barriers: distinguish catalysis, rate, and product control — Thermodynamics and reaction rates
- Gas particles: connect temperature, heat capacity, and nonideality — Fluids and gases
- Enolates: connect alpha-carbon chemistry to carbon–carbon bonds — Organic reaction reasoning
Psychology & Sociology — 71 lessons
- Sensory thresholds, adaptation, and habituation — Sensation and perception
- Classical conditioning: learn the predictive relationship — Learning and behavior change
- Operant learning: consequences and response patterns — Learning and behavior change
- Observational learning and reciprocal social influences — Learning and behavior change
- Signal detection: separate sensitivity from the decision rule — Sensation and perception
- Perception: organize the same input in different ways — Sensation and perception
- Attention under competing demands — Cognition and consciousness
- Problem solving, heuristics, and belief revision — Cognition and consciousness
- Memory systems, encoding, and neural plasticity — Cognition and consciousness
- Retrieval, interference, and reconstructed memory — Cognition and consciousness
- Emotion models and physiological evidence — Emotion and stress
- Stress appraisal, responses, and coping evidence — Emotion and stress
- Personality explanations and the situations they must explain — Individual influences on behavior
- Psychological disorder categories, context, and reported rates — Individual influences on behavior
- Motivation: compare needs, drives, arousal, and incentives — Individual influences on behavior
- When attitudes and behavior change one another — Individual influences on behavior
- An audience, a group, and individual performance — Social influence
- Conformity, authority, and social control — Social influence
- Norms, sanctions, and learning social expectations — Social influence
- Persuasion: message, audience, and processing conditions — Learning and behavior change
- Self-concept, self-efficacy, and perceived control — Self and identity
- Attribution: weigh the person and the situation — Social thinking
- Stereotypes, prejudice, stigma, and cultural interpretation — Social thinking
- Statuses, roles, and conflicting expectations — Social interaction
- Groups and networks: distinguish membership from connections — Social interaction
- Self-presentation, emotion signals, and audience — Social interaction
- Social bonds, helping, and aggression in context — Social interaction
- Discrimination: separate individual actions from institutional rules — Social interaction
- Sociological explanations and levels of analysis — Social structure and institutions
- Education, expectations, and unequal opportunities — Social structure and institutions
- Power, authority, economic organization, and work — Social structure and institutions
- Health, illness, and medicine as a social institution — Social structure and institutions
- Culture, symbols, and shared meaning — Social structure and institutions
- Sex, gender, orientation, and demographic measures — Demography and social change
- Race, ethnicity, and changing social classification — Demography and social change
- Migration, population change, and immigration status — Demography and social change
- Population pyramids and demographic change — Demography and social change
- Fertility and mortality: choose the right denominator — Demography and social change
- Social class, status, and different forms of capital — Social inequality and health
- Social reproduction, mobility, and claims of meritocracy — Social inequality and health
- Poverty, exclusion, and intersecting social positions — Social inequality and health
- Spatial inequality, environmental exposure, and access — Social inequality and health
- Vision from retinal input to features and pathways — Sensation and perception
- Hearing: translate vibration into an auditory code — Sensation and perception
- Touch, pain, body position, and balance — Sensation and perception
- Taste, smell, and evidence for chemical signals — Sensation and perception
- Cognitive development across tasks and the lifespan — Cognition and consciousness
- Intelligence theories and patterns of measured ability — Cognition and consciousness
- Consciousness, sleep stages, and circadian patterns — Cognition and consciousness
- Psychoactive effects, reward, and addiction — Cognition and consciousness
- Language learning, cognition, and brain evidence — Cognition and consciousness
- What brain methods can tell us about behavior — Individual influences on behavior
- Behavioral genetics: separate inherited variation from context — Individual influences on behavior
- Physiological development and changing behavior — Individual influences on behavior
- Anxiety, trauma-related responses, and compulsive behavior — Individual influences on behavior
- Mood episodes, psychotic symptoms, and biological explanations — Individual influences on behavior
- Group decisions: preference shifts and suppressed alternatives — Social influence
- Deviance, labels, and collective behavior — Social influence
- Identity development through people, groups, and culture — Self and identity
- Organizations, bureaucracy, and concentrated decision power — Social interaction
- Animal social behavior: costs, benefits, and signals — Social interaction
- Family, kinship, and changing household roles — Social structure and institutions
- Religion as a social institution — Social structure and institutions
- Cultural change, contact, and transmission — Social structure and institutions
- Aging, cohorts, and the life course — Demography and social change
- Social movements: grievances, organization, and strategy — Demography and social change
- Globalization: interdependence and competing explanations — Demography and social change
- Urbanization, neighborhood change, and population composition — Demography and social change
- Nervous-system disorders: connect functional changes to evidence — Individual influences on behavior
- Expectations, performance context, and warranted conclusions — Social thinking
- Health disparities and health-care disparities — Social inequality and health
Research & Data — 17 lessons
- Experimental Controls: What a Comparison Can Show — Design a study
- Psychological Measurement: What Does the Score Mean? — Design a study
- Hypotheses, predictions, and competing explanations — Design a study
- Observational and experimental studies: what can we conclude? — Design a study
- Reading graphs: axes, scales, and the comparison that matters — Interpret data
- Mean, median, and spread: describing a dataset — Interpret data
- Normalized data, percent change, and fold change — Interpret data
- Accuracy, precision, and sources of measurement error — Interpret data
- Sampling, selection bias, and generalizability — Design a study
- Cross-sectional and longitudinal studies: separating age and cohort — Design a study
- Blinding, placebo conditions, and expectancy effects — Design a study
- Surveys, interviews, and ethnography: matching method to question — Design a study
- Research ethics: consent, privacy, and justified conclusions — Design a study
- Correlation and scatterplots: direction, strength, and hidden structure — Interpret data
- Confidence intervals, error bars, and sample size — Interpret data
- Statistical significance and effect size: what the result means — Interpret data
- Reading a multi-figure experiment from claim to conclusion — Connect evidence
CARS — 17 lessons
- CARS Argument Analysis: Follow the Author’s Position — Evaluate an argument
- CARS main idea: finding the claim and its limits — Build comprehension
- CARS argument structure: paragraph roles and organization — Build comprehension
- CARS analogies and application: transferring the author’s principle — Reason beyond the text
- CARS passage walkthrough: restoration and originality — Humanities: art and philosophy
- CARS words in context: meaning, transitions, and qualifications — Build comprehension
- CARS tone and rhetoric: reading approval, doubt, and irony — Build comprehension
- CARS inference and assumptions: what must the argument rely on? — Evaluate an argument
- CARS evidence and causality: judging the support for a claim — Evaluate an argument
- CARS new evidence: strengthening, weakening, and revising a claim — Reason beyond the text
- CARS passage walkthrough: translation and meaning — Humanities: literature and language
- CARS passage walkthrough: archives and historical evidence — Social sciences: history
- CARS passage walkthrough: education and measurement — Social sciences: education
- CARS passage walkthrough: public space and design — Humanities: architecture
- CARS passage walkthrough: tradition and musical interpretation — Humanities: music and criticism
- CARS passage walkthrough: shared resources and incentives — Social sciences: economics and political science
- CARS passage walkthrough: maps and social boundaries — Social sciences: geography and anthropology
Use a short study path
These paths reuse the same canonical lessons. Start with one when you want a sequence instead of a topic lookup.
Core paths
From amino acids to protein experiments
Use molecular properties to interpret protein behavior and purification evidence.
From a rate curve to a mechanism
Connect the existing kinetics lesson to regulation, valid comparisons, and normalized results.
From solutions to buffers
Build a quantitative acid–base explanation and apply it to amino acid charge.
View the 6-lesson path
- Moles, formulas, and yield: conserve the reacting material
- Aqueous ions and concentration: keep amount and volume separate
- Acid–base strength: distinguish concentration from dissociation
- Weak acids, bases, and salts: choose a defensible pH calculation
- Buffers: explain pH resistance and its limits
- Amino acid and peptide charge: count the groups that can change
From measurement to learning
Use behavioral evidence to distinguish adaptation, predictive associations, consequences, and learning from a model.
Read a study and its figures
Follow a question through its design, graph, normalization and statistical description.
View the 6-lesson path
- Hypotheses, predictions, and competing explanations
- Experimental Controls: What a Comparison Can Show
- Observational and experimental studies: what can we conclude?
- Reading graphs: axes, scales, and the comparison that matters
- Normalized data, percent change, and fold change
- Mean, median, and spread: describing a dataset
CARS: from comprehension to transfer
Identify a position, test its structure, and transfer its principle to a new text.
Extended paths
From a gene to a functional result
Trace information flow and interpret an experiment that changes gene expression.
From fuel to ATP
Track energy and reducing equivalents from carbohydrates to oxidative phosphorylation.
From forces to fluid flow
Select the physical model that explains pressure, speed and flow resistance.
View the 6-lesson path
- Motion: translate between vectors, units, and graphs
- Net force and friction: build the right free-body diagram
- Work, energy, and power: choose the useful conservation model
- Pressure, buoyancy, and the role of fluid interfaces
- Ideal fluid flow: use continuity before Bernoulli
- Viscous flow: explain pressure loss and radius dependence
From a membrane to a neural signal
Connect membrane properties and gradients to signal propagation and synaptic integration.
From a dataset to a supported claim
Interpret variability and uncertainty before combining evidence from multiple figures.
View the 6-lesson path
- Reading graphs: axes, scales, and the comparison that matters
- Mean, median, and spread: describing a dataset
- Accuracy, precision, and sources of measurement error
- Confidence intervals, error bars, and sample size
- Statistical significance and effect size: what the result means
- Reading a multi-figure experiment from claim to conclusion
From social structure to health inequality
Apply sociological explanations to resources, mobility, place, and unequal health outcomes.
View the 6-lesson path
- Sociological explanations and levels of analysis
- Social class, status, and different forms of capital
- Social reproduction, mobility, and claims of meritocracy
- Poverty, exclusion, and intersecting social positions
- Spatial inequality, environmental exposure, and access
- Health disparities and health-care disparities
Connect the library to your study plan
Use explanations during Stage 1: Core Concepts. Use worked applications and answer-specific checks during Stage 2: Practice-Based Learning. Revisit changed conditions before reopening feedback so the lesson becomes a reasoning drill rather than passive review.
For the broader preparation sequence, use Aim High, Score Higher or the MCAT roadmap.
Official resources for broader practice
The AAMC content outline defines the tested content and reasoning skills. Use DDQX lessons for explanation and application, then use official AAMC materials for exam-level practice and calibration.
Official MCAT content outline · Official free MCAT resources