Chemistry of Life: Lesson 4 Summary

Collection of vocabulary terms and definitions related to key chemical concepts in biology.

Atom

The smallest structural unit of matter.

Molecule

Two or more atoms bound together.

Element

A substance consisting of one type of atom.

Compound

Two or more different elements bound together chemically.

Ion

An atom or molecule with a net electric charge due to electron gain or loss.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Radical

Species with unpaired electrons, highly reactive.

Atomic number (Z)

Number of protons in the nucleus.

Mass number (A)

Total number of protons and neutrons in the nucleus.

Octet rule

Atoms tend to have eight electrons in their outermost shell for stability.

Ionic bond

Attraction between oppositely charged ions.

Covalent bond

Sharing of electrons between atoms.

Hydrogen bond

A weak interaction between a hydrogen atom bonded to a highly electronegative atom and another electronegative atom.

Exergonic reaction

A reaction that releases energy.

Endergonic reaction

A reaction that requires input of energy to proceed.

Activation energy

The energy barrier that must be overcome for a reaction to start.

Dehydration synthesis

A process where two molecules join with the loss of a water molecule to form a larger molecule.

Hydrolysis

A process where a large molecule is broken into smaller units by adding water.

Buffer

A system that resists pH change by neutralizing added acid or base.

Homeostasis

Maintaining internal stability in cells and organisms.

Enzyme

A protein catalyst that lowers activation energy.

Osmosis

Diffusion of water across a semipermeable membrane.

Isotonic solution

A solution where the solute concentration outside equals that inside the cell.

Hypotonic solution

A solution with a lower solute concentration outside the cell, causing water influx.

Hypertonic solution

A solution with a higher solute concentration outside the cell, causing water efflux.

Acid

A substance that donates protons (H+) in solution.

Base

A substance that accepts protons (or donates OH− in some definitions).