AP Biology | Key Terms | 573 words

oxygen

A chemical element essential for life, represented by the symbol O.

carbon

A fundamental element in organic molecules, symbol C.

hydrogen

The lightest and most abundant chemical element, symbol H.

nitrogen

A key component of amino acids and nucleic acids, symbol N.

trace elements

Minerals required by organisms in minute quantities.

atom

The smallest unit of a chemical element.

protons

Positively charged subatomic particles found in the nucleus of an atom.

neutrons

Neutral particles in an atom's nucleus.

electrons

Negatively charged subatomic particles that orbit the nucleus of an atom.

nucleus

The central part of an atom that contains protons and neutrons.

isotopes

Variants of a chemical element that have the same number of protons but different numbers of neutrons.

radiometric dating

A method used to date materials based on the decay of radioactive isotopes.

compound

A substance formed when two or more elements are chemically bonded together.

chemical reaction

A process that involves rearrangement of the molecular or ionic structure of a substance.

chemical bond

The lasting attraction between atoms, ions, or molecules.

ionic bond

A chemical bond formed by the electrostatic attraction between oppositely charged ions.

covalent bond

A bond formed when two atoms share one or more pairs of electrons.

hydrogen bond

Weak bonds between hydrogen atoms and electronegative elements.

ions

Atoms or molecules that have gained or lost one or more electrons and have a charge.

nonpolar covalent

A type of covalent bond where electrons are shared equally between atoms.

polar covalent

A type of covalent bond where electrons are shared unequally between atoms.

polar

Molecules with a distribution of charge leading to positive and negative poles.

cohesion

The attraction between molecules of the same substance.

adhesion

The attraction between molecules of different substances.

surface tension

The cohesive force at the surface of a liquid that makes it behave as a stretched elastic membrane.

high heat capacity

The ability of a substance to absorb heat without significantly changing temperature.

expansion on freezing

The phenomenon where water expands as it freezes, causing ice to float.

adhesive

Substances that cause adherence or stickiness.

capillary action

The ability of a liquid to flow in narrow spaces without the assistance of external forces.

glycerol

A simple polyol compound that is a component of triglycerides.

acidic

Having a pH less than 7; characterized by the presence of excess hydrogen ions.

basic

Having a pH greater than 7; characterized by the presence of hydroxide ions.

neutral

Having a pH of 7; neither acidic nor basic.

alkaline

Relating to or having a pH greater than 7.

pH scale

A logarithmic scale used to specify the acidity or basicity of an aqueous solution.

organic compounds

Compounds that contain carbon, typically also hydrogen.

inorganic compounds

Compounds that do not primarily consist of carbon and hydrogen.

polymer

Large molecules composed of many repeated subunits (monomers).

monomer

A small, simple molecule that can join together to form polymers.

dehydration synthesis

A chemical reaction that involves the loss of water to form a bond.

condensation

The process of combining two molecules with the removal of water.

hydrolysis

The chemical breakdown of a compound due to reaction with water.

carbohydrates

Organic compounds made up of carbon, hydrogen, and oxygen in a 1:2:1 ratio.

monosaccharides

The simplest form of carbohydrates, consisting of single sugar molecules.

disaccharides

Carbohydrates formed from the combination of two monosaccharides.

polysaccharides

Complex carbohydrates formed by long chains of monosaccharide units.

glucose

A simple sugar that is an important energy source in living organisms.

fructose

A monosaccharide sugar found in many plants.

glycosidic linkage

The bond formed between carbohydrate molecules through a dehydration reaction.

starch

A complex carbohydrate consisting of a large number of glucose units.

cellulose

A polysaccharide comprising a chain of linked glucose units, forming the cell wall of plants.

glycogen

A form of energy storage in animals, consisting of a branched polysaccharide.

amino acids

Organic compounds that serve as the building blocks of proteins.

amino group

A functional group composed of one nitrogen atom bonded to two hydrogen atoms.

carboxyl group

A functional group consisting of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group.

R-group

The side chain component of an amino acid that determines its characteristics.

side chain

The variable part of an amino acid that distinguishes it from others.

hydrophobic

Water-repelling; tending to repel or fail to mix with water.

hydrophilic

Water-attracting; tending to mix with, dissolve in, or be wetted by water.

ionic

Relating to ions or the bond between them.

dipeptide

A molecule consisting of two amino acids joined by a peptide bond.

peptide bond

The covalent bond that links amino acids together.

polypeptide

A chain of amino acids linked by peptide bonds.

protein

Large biomolecules made up of one or more polypeptides.

primary structure

The sequence of amino acids in a polypeptide chain.

secondary structure

The localized folding of a polypeptide into alpha helices and beta sheets.

tertiary structure

The overall 3D shape of a polypeptide chain.

quaternary structure

The arrangement of multiple polypeptide chains into a single functional protein.

chaperon proteins (chaperonins)

Proteins that assist in the proper folding of other proteins.

lipids

A diverse group of hydrophobic molecules that include fats, oils, and phospholipids.

triglycerides

Lipids formed from glycerol and three fatty acids.

phospholipids

A type of lipid that forms cell membranes, composed of two fatty acids and a phosphate group.

steroids

Lipids characterized by a carbon skeleton with four fused rings.

ester linkage

The bond formed by a condensation reaction between a glycerol and a fatty acid.

saturated

Fatty acids with no double bonds between carbon atoms.

unsaturated

Fatty acids with one or more double bonds.

polyunsaturated

Fatty acids with multiple double bonds.

amphipathic molecule

A molecule that has both hydrophilic and hydrophobic parts.

cholesterol

A type of lipid that is an essential component of cell membranes.

nucleic acids

Biomolecules essential for all known forms of life, including DNA and RNA.

nucleotides

The building blocks of nucleic acids, consisting of a nitrogenous base, a sugar, and a phosphate group.

deoxyribonucleic acid (DNA)

The molecule that carries genetic information in living organisms.

ribonucleic acid (RNA)

A nucleic acid involved in the coding, decoding, regulation, and expression of genes.

cells

The basic structural and functional units of all living organisms.

surface area-to-volume ratio

The ratio that explains how the size and shape of a cell affects its ability to absorb nutrients and expel waste.

light microscopes

Optical instruments that use visible light to magnify images of small samples.

electron microscopes

Microscopes that use electron beams to achieve higher resolution than light microscopes.

prokaryotic cells

Single-celled organisms without a nucleus or membrane-bound organelles.

eukaryotic cells

Organisms with complex cells that contain a nucleus and membrane-bound organelles.

cytoplasm

The jelly-like fluid within a cell that contains organelles.

nucleoid

An irregularly shaped region within a prokaryotic cell that contains genetic material.

cell wall

A rigid outer layer that surrounds some cells and provides structural support.

plasma membrane

The biological membrane that separates and protects the interior of the cell from the external environment.

flagella

Long, whip-like structures that help with cellular movement.

capsule

A sticky outer coating that surrounds some bacteria, aiding in protection and adherence.

organelles

Specialized structures within a cell that perform distinct processes.

phospholipid bilayer

A double layer of phospholipids that makes up cell membranes.

peripheral proteins

Proteins that are loosely attached to the surface of a membrane.

integral proteins

Proteins that are embedded within and often span the entire membrane.

transmembrane proteins

Integral proteins that extend across the membrane.