General Biology Key Terms

The atomic number is the number of protons in an atom's nucleus.

An ionic bond forms when electrons are transferred between atoms, creating charged ions.

A covalent bond forms when atoms share one or more pairs of electrons.

A molecule is two or more atoms held together by covalent bonds.

An ion is an atom or molecule with a net electric charge due to loss or gain of electrons.

A hydrogen bond is a weak attraction between a hydrogen atom and an electronegative atom.

A polar molecule has an uneven distribution of charge, with partial positive and negative ends.

Cohesion is the attraction between molecules of the same substance.

Adhesion is the attraction between molecules of different substances.

Surface tension is the resistance of a liquid surface to external force due to cohesion.

Thermal energy is the total kinetic energy of particles in a substance.

Evaporative cooling occurs when the surface of a liquid cools as molecules with the highest energy evaporate.

A solution is a homogeneous mixture of two or more substances.

A solvent is the substance that dissolves the solute in a solution.

A solute is the substance dissolved in a solvent to form a solution.

An acid increases the hydrogen ion concentration in a solution and has a pH less than 7.

A base reduces the hydrogen ion concentration in a solution and has a pH greater than 7.

The pH scale measures the acidity or basicity of a solution, ranging from 0 to 14.

A buffer is a substance that minimizes changes in pH by accepting or donating hydrogen ions.

Organic compounds contain carbon atoms bonded to hydrogen and other elements.

Hydrophilic molecules are attracted to water and can dissolve in it.

Macromolecules are large molecules made of smaller subunits called monomers.

Polymers are long chains of repeating monomer units.

Monomers are small molecules that can join to form polymers.

Dehydration synthesis is the process of joining monomers by removing water.

Hydrolysis is the breakdown of polymers into monomers by adding water.

Enzymes are proteins that speed up chemical reactions by lowering activation energy.

Carbohydrates are organic molecules made of carbon, hydrogen, and oxygen, used for energy and structure.

Monosaccharides are simple sugars and the monomers of carbohydrates.

Glucose is a common monosaccharide used as an energy source.

A disaccharide is a carbohydrate made of two monosaccharides joined by a covalent bond.

Polysaccharides are long chains of monosaccharides used for energy storage or structural support.

Starch is a polysaccharide used by plants to store energy.

Glycogen is a polysaccharide used by animals to store energy.

Cellulose is a polysaccharide that provides structural support in plant cell walls.

Lipids are hydrophobic molecules used for long-term energy storage and membrane structure.

Hydrophobic molecules repel water and do not dissolve in it.

An unsaturated fatty acid has one or more double bonds and is usually liquid at room temperature.

A saturated fatty acid has no double bonds and is usually solid at room temperature.

Phospholipids are lipids with a hydrophilic head and two hydrophobic tails, forming cell membranes.

Cholesterol is a lipid that stabilizes cell membranes and serves as a precursor for steroids.

Proteins are polymers of amino acids that perform diverse functions in cells.

Denaturation is the loss of a protein's shape and function due to environmental changes.

Amino acids are the monomers that make up proteins.

A peptide bond is a covalent bond linking amino acids in a protein.

A polypeptide is a chain of amino acids linked by peptide bonds.

DNA stores genetic information in cells using a double helix structure.

RNA is involved in protein synthesis and gene expression, usually single-stranded.