AP Biology Comprehensive Vocabulary

A complete and comprehensive set of flashcards for all of the vocabulary assessed by the AP Biology exam as of 2026.

Independent variable

Variable that is changed by experimenter. Represented on the x-axis.

Dependent variable

Variable that is affected by the change in independent variable. Represented on the y-axis.

Control Variable

Held constant throughout the experiment.

Null hypothesis

Hypothesis proclaiming that there is no statistically significant change depending on change in independent variables.

Alternate hypothesis

Hypothesis proclaiming that there IS a statistically significant change when changing independent variables.

Experimental Group

Group that receives the independent variable in order to test it.

Control Group

Does not receive independent variables to compare results to the experimental group.

Mean

Add all data points together and divide by sample size.

Standard deviation

The square root of (Sum of (x - mean)^2 / (N - 1)).

Standard error of mean

Divide the standard deviation by the square root of the sample size.

Chi-Squares

Used to find if variances from predicted data are due to chance or not.

Degrees of freedom

The number of independent variables minus one.

Critical value

Value used to determine if a chi-square result allows for the rejection of the null hypothesis.

Bar graphs

Graphs typically used to compare data of different independent variables.

Error bars

Lines on a graph showing the standard error of the mean

Line graphs

Graphs that show continuous data such as time elapsed.

Box and Whisker Plots

Plots of all data points in a set showing the median, 25th and 75th percentiles, and range.

Behavior

The actions an organism performs when reacting to certain stimuli.

Innate Behavior

A behavior that is passed down through genetics

Learned Behavior

A behavior acquired through experience and observation.

Fixed Action Pattern

A simple response to a stimulus that is innate.

Kinesis

Random movements based on certain stimuli where the rate of movement changes.

Orthokinesis

Rate of movement proportional to the intensity of stimuli.

Klinokinesis

Rate of turning proportional to the intensity of stimuli.

Taxis

Innate behavior where an organism moves towards or away from a stimulus.

Habituation

Learned process where irrelevant stimuli no longer trigger a response over time.

Migration

Long distance movement of organisms that is primarily innate.

Classical Conditioning

Process where an organism learns to react to stimuli after multiple results

Operant Conditioning

Process where an organism associates a behavior with consequences and changes it based on results.

Imprinting

Rapid learning process where a species bonds with the first moving object they see after birth.

Proximate Cause

How a behavior happens.

Ultimate Cause

Why a behavior happens in an evolutionary context.

Polar Covalent Bond

A bond where electrons are shared unequally between atoms.

Hydrogen Bonds

Weak bonds between the positive hydrogen of one molecule and a negative atom of another.

Cohesion

The property of water molecules sticking to each other.

Adhesion

The property of water molecules sticking to other surfaces.

Surface Tension

A measure of how difficult it is to stretch or break the surface of a liquid.

Specific Heat

The amount of heat required to change the temperature of a substance.

Evaporative Cooling

Process where the surface of an object becomes cooler during evaporation.

Hydrophilic

Substances that have an affinity for water.

Hydrophobic

Substances that repel water.

Carbohydrates

Macromolecules made of monosaccharides used for energy and structure.

Monosaccharides

The simplest form of carbohydrates (monomers).

Polysaccharides

Complex carbohydrates made of many monosaccharides.

Lipids

Hydrophobic macromolecules including fats, phospholipids, and steroids.

Triglycerides

Fats made of glycerol and three fatty acids bonded by ester linkages.

Saturated Fats

Fats with no double bonds in their tails

Unsaturated Fats

Fats with double bonds that cause bending

Phospholipids

Lipids with a hydrophilic phosphate head and two hydrophobic fatty acid tails

Proteins

Macromolecules made of amino acid monomers that perform most cellular functions.

Amino Acids

Monomers of proteins containing a carboxyl group, amino group, and unique R group.

Polypeptides

Polymers of amino acids.

Primary Structure

The unique sequence of amino acids in a protein.

Secondary Structure

Coils (alpha helix) or folds (beta pleated sheets) in a polypeptide chain.

Tertiary Structure

Irregular folding of a protein due to R group interactions like disulfide bridges.

Quaternary Structure

Joining of two or more polypeptide chains into one macromolecule.

Chaperonins

Proteins that help fold polypeptides into the correct structure.

Nucleic Acids

DNA and RNA

Nucleotides

Monomers of nucleic acids made of a pentose sugar, phosphate group, and nitrogenous base.

Pyrimidines

Single-ringed nitrogenous bases including Cytosine, Thymine, and Uracil.

Purines

Double-ringed nitrogenous bases including Adenine and Guanine.

Prokaryotic Cells

Cells without membrane-bound organelles, typically Bacteria or Archaea.

Eukaryotic Cells

Cells with membrane-bound organelles such as Plants, Animals, and Fungi.

Plasma membrane

Organelle that separates the cell from the outside environment.

Cell Wall

Structural support found in plants, fungi, and some prokaryotes.

Nucleus

Organelle that stores genetic information in eukaryotic cells.

Nucleolus

Structure inside the nucleus that produces ribosomes.

Mitochondria

Powerhouse of the cell

Chloroplast

Organelle that converts sunlight to chemical energy via photosynthesis.

Lysosomes

Organelles that break down macromolecules and destroy cellular invaders.

Ribosomes

Structures that synthesize proteins.

Smooth ER

Part of the endoplasmic reticulum that assembles and modifies lipids.

Rough ER

Part of the endoplasmic reticulum that modifies proteins and has ribosomes on the outside.

Golgi apparatus

Organelle that packages proteins to be sent inside or outside the cell.

Cytoskeleton

Protein strands that stabilize the structure of the cell.

Surface Area to Volume Ratio

Ratio that determines cell efficiency

Osmosis

Passive transport of water from low to high solute concentration.

Hypertonic

A solution with a higher solute concentration than the cell

Hypotonic

A solution with a lower solute concentration than the cell

Isotonic

Equal solute concentration

Water Potential

The potential for water to move

Solute Potential

Calculated by the formula -iCRT.

Endocytosis

How cells take in substances by creating a vacuole from the membrane.

Phagocytosis

The process of a cell taking in solid materials (cell eating).

Pinocytosis

The process of a cell taking in liquid (cell drinking).

Exocytosis

Releasing substances from the cell via vesicles.

Endosymbiote Theory

Theory that mitochondria and chloroplasts originated from engulfed prokaryotes.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transferred or transformed.

Second Law of Thermodynamics

Every energy transfer increases the entropy of the universe.

Catabolic Pathways

Pathways that break down molecules and release energy (exergonic).

Anabolic Pathways

Pathways that consume energy to build molecules (endergonic).

Enzymes

Biological catalysts that speed up reactions by lowering activation energy.

Substrate

The reactant an enzyme acts on.

Active Site

The region on the enzyme where the substrate binds.

Competitive Inhibitors

Molecules that bind to the active site to compete with the substrate.

Noncompetitive Inhibitors

Molecules that bind elsewhere on the enzyme to change its shape and block function.

Cellular Respiration

The process of breaking down glucose to produce ATP.

Glycolysis

First step of respiration

Krebs Cycle

Occurs in mitochondrial matrix

Electron Transport Chain

Series of proteins in the inner mitochondrial membrane that creates a proton gradient.