AP Biology: Key Terms

Covalent bond

(Chemistry) A bond formed when two atoms share electrons.

Hydrogen bond

(Chemistry) A weak attraction between a hydrogen atom and an electronegative atom.

pH

(Chemistry) A measure of hydrogen ion concentration; the acidity or basicity of a solution.

Carbohydrate

(Macromolecules) An organic molecule of sugars used for energy and structure.

Protein

(Macromolecules) A polymer of amino acids that carries out most cellular functions.

Enzyme

(Macromolecules) A protein that speeds up a reaction by lowering its activation energy.

Lipid

(Macromolecules) A hydrophobic molecule such as fats and phospholipids.

Nucleic acid

(Macromolecules) A polymer (DNA or RNA) that stores genetic information.

Prokaryote

(Cells) A cell lacking a nucleus and membrane-bound organelles.

Eukaryote

(Cells) A cell with a nucleus and membrane-bound organelles.

Mitochondrion

(Cells) The organelle that produces ATP through cellular respiration.

Chloroplast

(Cells) The organelle where photosynthesis occurs in plant cells.

Cell membrane

(Cells) The phospholipid bilayer that controls what enters and exits a cell.

Diffusion

(Transport) The movement of molecules from high to low concentration.

Osmosis

(Transport) The diffusion of water across a selectively permeable membrane.

Active transport

(Transport) Movement of molecules against their gradient using energy (ATP).

ATP

(Energy) The molecule that stores and supplies energy for cellular work.

Cellular respiration

(Energy) The process of breaking down glucose to produce ATP.

Photosynthesis

(Energy) The process by which plants convert light energy into glucose.

Glycolysis

(Energy) The breakdown of glucose into pyruvate in the cytoplasm.

Mitosis

(Cell division) Division producing two genetically identical diploid cells.

Meiosis

(Cell division) Division producing four genetically varied haploid gametes.

DNA

(Genetics) The double-helix molecule that carries genetic instructions.

Replication

(Genetics) The copying of DNA before cell division.

Transcription

(Genetics) The synthesis of RNA from a DNA template.

Translation

(Genetics) The synthesis of a protein from mRNA at the ribosome.

Gene

(Genetics) A segment of DNA that codes for a protein or trait.

Allele

(Genetics) An alternative form of a gene.

Genotype

(Genetics) The genetic makeup of an organism.

Phenotype

(Genetics) The observable physical traits of an organism.

Dominant allele

(Genetics) An allele expressed when at least one copy is present.

Recessive allele

(Genetics) An allele expressed only when two copies are present.

Mutation

(Genetics) A change in the DNA sequence.

Natural selection

(Evolution) The process by which favorable traits become more common over generations.

Adaptation

(Evolution) An inherited trait that improves survival and reproduction.

Speciation

(Evolution) The formation of a new species.

Hardy-Weinberg equilibrium

(Evolution) A state in which allele frequencies stay constant without evolutionary forces.

Homeostasis

(Systems) The maintenance of a stable internal environment.

Negative feedback

(Systems) A response that counteracts a change to restore balance.

Ecosystem

(Ecology) A community of organisms together with their physical environment.

Producer

(Ecology) An organism that makes its own food, usually via photosynthesis.

Food web

(Ecology) The interconnected feeding relationships in an ecosystem.

Carrying capacity

(Ecology) The maximum population size an environment can sustain.

Biodiversity

(Ecology) The variety of life in an ecosystem or on Earth.

Carbon cycle

(Ecology) The movement of carbon through organisms, the atmosphere, and the earth.