Free MCAT Study Tools by AAMC Content Category

1A: Structure and function of proteins and their constituent amino acids

Biological and Biochemical Foundations of Living Systems, Foundational Concept 1: amino acid structure, side chain classes, charge and isoelectric point, and enzyme kinetics with Michaelis-Menten curves and competitive, noncompetitive and uncompetitive inhibition.

• Biology Enzyme Kinetics Simulator Km and Vmax, and how each inhibitor changes them.
• Biology Amino Acid 3D Explorer All 20 amino acids in 3D, grouped by side chain, their charges changing as you move the pH.

1B: Transmission of genetic information from the gene to the protein

Foundational Concept 1: the double helix and base pairing, transcription and translation through the genetic code, and the biotechnology the outline lists, from the polymerase chain reaction and gel electrophoresis to the analysis of gene expression by qPCR.

• Biology Protein Synthesis Simulator Type a gene and watch RNA polymerase, a ribosome and tRNAs build its protein, step by step.
• Biology PCR Simulator Watch PCR cycle by cycle, find where primers bind on a typed template, and run the product on a gel.
• Biology Gel Electrophoresis Simulator Run a virtual agarose gel with a ladder and digests, and size an unknown band from the semi-log standard curve.
• Biology qPCR and ΔΔCt Simulator Four Ct values to a fold change by 2^−ΔΔCt or Pfaffl, with amplification curves, a threshold and a standard curve.
• Biology DNA Double Helix Explorer The grooves, and the strand offset that creates them.
• Biology DNA to Protein Translator Paste DNA or mRNA and read off the protein, codon by codon, in every reading frame.

1C: Transmission of heritable information from generation to generation and the processes that increase genetic diversity

Foundational Concept 1: Mendelian crosses, codominance and multiple alleles in the ABO blood groups, sex-linked inheritance, the Hardy-Weinberg principle, and the chi-square test that checks a cross against its expected ratio.

• Biology Punnett Square Calculator Genotype and phenotype ratios for crosses of up to three genes, with the square drawn.
• Biology Blood Type and X-Linked Punnett Square Calculator A child’s possible ABO and Rh types from the parents’, and X-linked crosses split by sons and daughters.
• Biology Hardy-Weinberg Calculator Allele and genotype frequencies from one known value or from counts, with a chi-square test of equilibrium.
• Maths & Data Chi-Square Calculator Goodness of fit and contingency tables, with expected counts, p-value, critical values and working.

2A: Assemblies of molecules, cells, and groups of cells within single cellular and multicellular organisms

Foundational Concept 2: the membrane-bound organelles that define eukaryotic cells, and solute transport across the plasma membrane by diffusion and osmosis.

• Biology Diffusion and Osmosis Simulator Diffusion or osmosis across one membrane, counted against Fick’s law.
• Biology Cell Structure Explorer Labelled animal and plant cells, with what every organelle is, does and measures.

2B: The structure, growth, physiology, and genetics of prokaryotes and viruses

Foundational Concept 2: bacteria classified by shape and by the Gram stain, which sorts them by cell wall, and the exponential growth of a population dividing by fission.

• Biology Bacterial Unknown Identification Lab Run standard tests on 15 teaching bacteria, or enter your own results, and watch a dichotomous key narrow the field.
• Biology Cell Doubling Time Calculator Doubling time and growth rate from two counts, or project forward.

2C: Processes of cell division, differentiation, and specialization

Foundational Concept 2: the phases of mitosis and how meiosis differs from it, with the chromosome and chromatid count at every stage.

• Biology Mitosis and Meiosis Explorer Mitosis and meiosis stage by stage, with chromosome and chromatid counts for your 2n.

3A: Structure and functions of the nervous and endocrine systems and ways these systems coordinate the organ systems

Foundational Concept 3: the resting potential from the Nernst and Goldman equations, the action potential with its threshold and refractory period, and the reflex arc through the spinal cord.

• Biology Resting Membrane Potential Simulator Nernst per ion, Goldman for the membrane.
• Biology Action Potential Simulator Hodgkin-Huxley, with threshold and refractoriness emerging.
• Biology Reflex Arc Simulator Tap the knee and follow the reflex arc from spindle to spinal cord to muscle, timed to the millisecond.

Reflex Arc Simulator: picture drawn from BodyParts3D, © The Database Center for Life Science, CC BY 4.0.

3B: Structure and integrative functions of the main organ systems

Foundational Concept 3: the four-chambered heart through one cardiac cycle, systolic and diastolic pressure, oxygen transport by hemoglobin, breathing and alveolar gas exchange, acid-base balance, the nephron’s counter-current multiplier, muscle contraction from twitch to tetanus, the female reproductive cycle, and the gross structure of the main organs.

• Biology Cardiac Cycle Simulator Pressures, volume, valves and ECG through one heartbeat.
• Biology Oxygen Dissociation Curve Simulator The sigmoid curve, and what moves it left or right.
• Biology Spirometry and Flow-Volume Loop Simulator Watch normal, obstructive, restrictive and upper airway flow-volume loops form, with FEV1/FVC read out.
• Biology Nephron Explorer The loop, the gradient it builds, and what ADH can do with it.
• Biology Muscle Twitch and Tetanus Simulator Fire a muscle at any frequency and watch single twitches sum into unfused and then fused tetanus.
• Biology Menstrual Cycle Hormone Simulator FSH, LH, estrogen and progesterone through the cycle, with the follicle and the lining redrawn each day.
• Biology Heart Explorer Heart wall, valves, papillary muscles and coronary vessels.
• Biology Internal Organs Explorer Lungs, gut, liver, kidneys and spleen, separable.
• Biology Mean Arterial Pressure Calculator MAP and pulse pressure from a blood pressure.
• Biology A-a Gradient and Alveolar Gas Equation Calculator Alveolar oxygen, the A-a gradient and P/F ratio.
• Biology Acid Base Interpreter A blood gas worked through, one reasoned step at a time.

Heart Explorer and Internal Organs Explorer: pictures drawn from BodyParts3D, © The Database Center for Life Science, CC BY 4.0.

4A: Translational motion, forces, work, energy, and equilibrium in living systems

Chemical and Physical Foundations of Biological Systems, Foundational Concept 4: motion in one and two dimensions, Newton’s laws, static and kinetic friction, torque, work, power, kinetic and potential energy, and periodic motion on a spring and a pendulum.

• Mechanics Projectile Motion Simulator Animate a trajectory and read off range, apex and flight time as you change launch speed and angle.
• Mechanics Inclined Plane Simulator Tilt a slope, set the friction and a push, and see whether the block slides, how fast, and where its energy goes.
• Mechanics Conservation of Energy Simulator A cart on a track you reshape, with kinetic, potential and thermal energy bars whose total never changes.
• Mechanics Mass Spring Simulator Simple harmonic motion with damping and a driving force, plus the resonance curve.
• Mechanics Simple Pendulum Simulator Swing a pendulum, add damping, and watch the small-angle approximation fail at large amplitude.
• Mechanics Free-Body Diagram Maker Draw the forces on a block, a hanging weight, a mass in a lift or your own set to scale, and read off the net force.
• Mechanics Kinematics Calculator Any three of u, v, a, s, t gives the other two, and it names the equation.
• Mechanics Force Calculator (F = ma) Force, mass or acceleration from F = ma, with g-force and weight.
• Mechanics Torque Calculator Torque from arm, force and angle, in N·m, lbf·ft and lbf·in.
• Mechanics Work and Power Calculator Work from force, distance and angle, plus the average power over a time.
• Mechanics Kinetic Energy Calculator Kinetic energy, mass or speed from KE = ½mv², plus momentum.
• Mechanics Gravitational Potential Energy Calculator PE = mgh solved any way round, with the impact speed for that drop.
• Mechanics Hooke’s Law Calculator Force, stiffness or extension from F = kx, plus the energy stored.

4B: Importance of fluids for the circulation of blood, gas movement, and gas exchange

Foundational Concept 4: density, buoyancy, pressure at depth, continuity, Bernoulli’s equation and turbulence, then the gas laws and the kinetic molecular theory of gases.

• Mechanics Buoyancy Simulator Lower a block into a liquid on a spring balance and watch the buoyant force share its weight.
• Thermodynamics Kinetic Theory Gas Simulator Atoms in a box, with the gas law measured rather than assumed.
• Mechanics Density Calculator Density, mass or volume in g/cm³ and kg/m³, with lb/ft³ in the reference table.
• Mechanics Pressure Calculator Solve P = F/A in mixed units and read the answer in atm, bar and psi at once.
• Mechanics Hydrostatic Pressure Calculator Absolute and gauge pressure at a depth from P = P₀ + ρgh.
• Mechanics Continuity Equation Calculator Speed or area across a pipe from A₁v₁ = A₂v₂, with the flow rate Q = Av.
• Mechanics Bernoulli Equation Calculator Pressure, speed or height at two points on a streamline from Bernoulli’s equation.
• Mechanics Reynolds Number Calculator Re = ρvD/μ for a pipe, with the flow regime and the kinematic viscosity.
• Thermodynamics Ideal Gas Law Calculator Solve PV = nRT for any variable, with kelvin conversion handled for you.
• Thermodynamics Boyle’s Law Calculator Squeeze or expand a gas at one temperature and get its new pressure or volume, plus the work done.
• Thermodynamics Charles’s Law Calculator Warm or cool a gas at constant pressure and get its new volume or temperature, with kelvin handled.
• Thermodynamics Combined Gas Law Calculator Relate pressure, volume and temperature between two states of a sealed gas.

4C: Electrochemistry and electrical circuits and their elements

Foundational Concept 4: Coulomb’s law and electric fields, Ohm’s law, resistivity and resistors in series and parallel, capacitor energy and capacitor networks, the Lorentz force on a moving charge, and galvanic cells built from reduction potentials and the Nernst equation.

• Electricity Series and Parallel Circuit Simulator Bulbs, switches and meters in series, parallel and bridge circuits, solved exactly.
• Electricity Electric Field Simulator Point charges you can drag, with field lines, equipotentials and a probe reading E and V.
• Electricity Charged Particle in a Magnetic Field Simulator Circles, helices, a velocity selector and a mass spectrometer, from the exact Lorentz force.
• Chemistry Galvanic Cell Simulator Two metals, two solutions and a salt bridge, run down while the voltage falls and the electrodes change mass.
• Chemistry Standard Reduction Potentials Half-reaction potentials, strongest oxidant first.
• Electricity Ohm’s Law Calculator Voltage, current or resistance from V = IR, plus power dissipation.
• Electricity Resistor Network Calculator Series and parallel networks, with the current in each resistor shown.
• Electricity Wire Resistance Calculator Conductor resistance from length and cross-section, plus the voltage drop.
• Electricity Coulomb’s Law Calculator Force between two point charges, plus the field one of them produces.
• Electricity Capacitor Energy Calculator Energy and charge stored in a capacitor from capacitance and voltage.
• Electricity Capacitors in Series and Parallel Calculator Series, parallel and mixed capacitor networks, with the charge on each capacitor.
• Chemistry Nernst Equation Calculator Cell potential from two half-reactions at any concentration and temperature, with the free energy, K and the working.

4D: How light and sound interact with matter

Foundational Concept 4: sound intensity in decibels, the Doppler effect and resonance on a string; interference, the electromagnetic spectrum and photon energy; refraction, dispersion, total internal reflection and thin lenses; and spin-spin splitting in NMR.

• Waves & Optics Doppler Effect Simulator Wavefronts from a moving source, and the shift they produce.
• Waves & Optics Standing Wave Simulator Harmonics on a string, with the two travelling waves that superpose to make them.
• Waves & Optics Double Slit Simulator Interference fringes, and the single-slit envelope shaping them.
• Waves & Optics Wave Interference Simulator Two coherent sources, their nodal lines, and the path difference at any point.
• Waves & Optics Refraction Simulator Rays through a boundary, a glass block and a prism, with total internal reflection and white light split into colours.
• Waves & Optics Ray Diagram Simulator The three principal rays, with the image located where they cross.
• Waves & Optics Electromagnetic Spectrum Explorer Radio waves to gamma rays on one scale, with wavelength, frequency and photon energy linked.
• Chemistry NMR Splitting Pattern Visualizer Choose neighbours and coupling constants to draw the splitting tree and see the multiplet it makes, line by line.
• Waves & Optics Decibel Calculator Sound level from intensity, with distance falloff and safe exposure time.
• Waves & Optics Wavelength and Frequency Calculator Wavelength to frequency and back, for light, sound or any wave speed.
• Waves & Optics Photon Energy Calculator Photon energy from wavelength, in eV, joules and kJ per mole.
• Waves & Optics Snell’s Law Calculator Solve n₁sinθ₁ = n₂sinθ₂ for any term, with the critical angle shown for the pair of media.
• Waves & Optics Thin Lens Calculator Solve the thin lens equation and get magnification with the image type spelled out.

4E: Atoms, nuclear decay, electronic structure, and atomic chemical behavior

Foundational Concept 4: protons, neutrons and isotopes, half-life and radioactive decay, the Bohr atom and line spectra, orbitals, electron configurations and the photoelectric effect, plus the stoichiometry the outline files here, from molecular weight and empirical formulas to balanced equations, limiting reactants and theoretical yield.

• Chemistry Radioactive Decay Simulator Individual nuclei decaying at random, against the curve the formula predicts.
• Chemistry Bohr Model and Hydrogen Spectrum Simulator Jump an electron between Bohr orbits and read the photon’s energy, wavelength and series.
• Chemistry Flame Test and Emission Spectrum Simulator Hold a salt in the flame, see its colour, and split it into the lines and bands that make it.
• Waves & Optics Photoelectric Effect Simulator Which light frees electrons from a metal, how fast they leave, and what stops them.
• Chemistry Atomic Orbitals Visualizer Orbital shapes from the exact wavefunction, turnable, with every node counted.
• Chemistry Periodic Table Interactive periodic table of all 118 elements, with IUPAC atomic masses.
• Chemistry Protons, Neutrons and Electrons Calculator Protons, neutrons and electrons for any isotope or ion, with the nuclide symbol.
• Chemistry Half-Life Calculator Remaining amount, elapsed time or half-life for any decay process.
• Chemistry Electron Configuration Calculator Configurations of elements and ions in full and noble gas notation, with orbital boxes and unpaired electrons.
• Chemistry Molar Mass Calculator Type any formula, including hydrates, and get molar mass, percent composition and grams to moles or particles.
• Chemistry Empirical Formula Calculator Empirical formula from composition, plus the molecular formula from molar mass.
• Chemistry Chemical Equation Balancer Balance any equation, ions and half-equations included, with the working and an atom count.
• Chemistry Stoichiometry Calculator Grams to grams, moles and gas volumes through a balanced equation.
• Chemistry Limiting Reagent Calculator Limiting reagent, theoretical yield and percent yield in one pass.
• Chemistry Percent Yield Calculator Percent yield from actual and theoretical mass, with the shortfall.

5A: Unique nature of water and its solutions

Foundational Concept 5: common ions and their charges, the pH of strong and weak acids and bases, buffers and the Henderson-Hasselbalch equation, molarity, and titration from the indicator endpoint to the full curve.

• Chemistry Titration Lab Simulator A burette, an indicator and an exact pH meter, with your endpoint measured against equivalence.
• Chemistry Polyatomic Ions Common polyatomic ions by charge, with formulae, names and computed molar masses.
• Chemistry pH Calculator pH, pOH, [H⁺] and [OH⁻] for strong or weak acids and bases, solved exactly.
• Chemistry Henderson-Hasselbalch Calculator Buffer pH from the acid-base ratio, or the ratio needed for a target pH.
• Chemistry Titration Curve Calculator An exact titration curve, with the equivalence pH and the indicator to match it.
• Chemistry Titration Calculator Find an unknown concentration from endpoint volume, with the stoichiometric ratio applied.
• Chemistry Molarity Calculator Solve for any one of concentration, mass, molar mass or volume, with units from nM to M.

5B: Nature of molecules and intermolecular interactions

Foundational Concept 5: Lewis structures with formal charge and resonance, VSEPR shapes, R and S configuration by the Cahn-Ingold-Prelog rules, and conformational isomers in Newman projections and cyclohexane chairs.

• Chemistry Lewis Structure Generator Type a formula or ion and watch its Lewis structure build, with formal charges and resonance.
• Chemistry VSEPR Molecular Geometry Lone pairs drawn, so the shape has a visible reason.
• Chemistry R and S Configuration Explorer Rank four groups by the CIP rules, turn the stereocentre until group 4 points away, and read R or S from the arrow.
• Chemistry Newman Projection and Conformation Explorer Turn a C−C bond and watch the Newman projection, the sawhorse and the energy curve follow.
• Chemistry Cyclohexane Chair Conformation Explorer Flip a substituted cyclohexane chair and see which chair wins, by how many kJ/mol, and the ratio at any temperature.

5C: Separation and purification methods

Foundational Concept 5: chromatography on the two column methods the outline names, gas-liquid and high-pressure liquid chromatography, with retention time and resolution changing as the solvent, oven temperature or column changes.

• Chemistry HPLC and GC Chromatography Simulator Watch two to four analytes separate on an HPLC or GC column, with retention times, plate count and resolution.

5E: Principles of chemical thermodynamics and kinetics

Foundational Concept 5: calorimetry and specific heat, heats of fusion and vaporization, the coefficient of expansion, work as the area on a PV diagram, Gibbs free energy and spontaneity, and kinetics from rate laws and reaction order to activation energy, the Arrhenius equation and equilibrium constants.

• Thermodynamics Heat Engine and Carnot Cycle Simulator Run a gas around a thermodynamic cycle and read the work off the enclosed area.
• Chemistry Collision Theory and Activation Energy Simulator See how few molecules clear the activation barrier, and why heating changes that so violently.
• Thermodynamics Calorimetry Calculator Heat, mass, specific heat or ΔT from q = mcΔT, in joules or calories.
• Thermodynamics Heating Curve Calculator Energy from ice to steam, counting every stage a single m c dT misses.
• Thermodynamics Latent Heat Calculator Heat to melt or boil a mass, and why the thermometer stops moving.
• Thermodynamics Thermal Expansion Calculator Length change from a temperature change, plus the stress if it cannot move.
• Thermodynamics Gibbs Free Energy Calculator ΔG from ΔH, T and ΔS, or any one of them, with the spontaneity verdict, the crossover temperature and K.
• Chemistry Integrated Rate Law Calculator Concentration, time, rate constant and half-life at zero, first and second order, and the order from data.
• Chemistry Arrhenius Equation Calculator Find a reaction’s activation energy from two rate constants, or its rate constant at a new temperature.
• Chemistry ICE Table Calculator Fill in an ICE table, solve for x exactly and test the small-x shortcut, or find K from equilibrium amounts.

6A: Sensing the environment

Psychological, Social, and Biological Foundations of Behavior, Foundational Concept 6: the structure and function of the eye, the visual pathways in the brain, the three cone types and what changes when one is shifted or missing, and hearing, from the hair cells of the cochlea to the range of pitch they detect.

• Biology Color Blindness Simulator Any image as protan, deutan or tritan eyes see it, at any severity, with the cone curves that explain why.
• Biology Hearing Range Test and Hearing Loss Simulator Find the highest pitch you can hear, see each pitch as a place on the cochlea, and hear music through a hearing loss.
• Biology Blind Spot Mapper Watch a dot vanish, as Mariotte’s paper did in 1668, then map your own blind spot in degrees and see it as the optic disc on the retina.
• Biology Visual Field Defects Explorer Place a lesion anywhere from optic nerve to visual cortex and see each eye’s field loss, named and explained.

6B: Making sense of the environment

Foundational Concept 6: the stages of sleep and how the cycles change across a night, with deep sleep concentrated early and REM sleep late.

• Biology Sleep Cycle and Hypnogram Visualizer A typical night’s sleep stages from your bedtime to your alarm, with deep sleep early, REM late and the windows where waking is easiest.

7A: Individual influences on behavior

Foundational Concept 7: the biological bases of behavior, from the forebrain, midbrain and hindbrain to the limbic structures and the cerebral lobes, as named structures in a 3D brain.

• Biology Brain Explorer 101 brain structures, gyri to ventricles, separable.

Brain Explorer: picture drawn from BodyParts3D, © The Database Center for Life Science, CC BY 4.0.