2.1 Atoms, Ions, and Molecules — Vocabulary Flashcards

Vocabulary flashcards covering key terms from the notes on atoms, ions, molecules, water, mixtures, pH, energy, metabolism, organic compounds, carbohydrates, lipids, proteins, nucleic acids, and enzymes.

Element

The simplest form of matter with unique chemical properties (water is not an element).

Atomic number

Number of protons in an atom's nucleus; identifies the element.

Proton

Positively charged subatomic particle in the nucleus.

Neutron

Electrically neutral subatomic particle in the nucleus.

Electron

Negatively charged subatomic particle surrounding the nucleus; determines chemical properties.

Symbol

One- or two-letter abbreviation that represents an element.

Isotope

Variants of an element differing in neutron number and atomic mass.

Radioisotope

Radioactive isotope that decays and emits radiation.

Half-life

Time required for 50% of a radioisotope to decay.

Ion

Charged particle formed when electrons are transferred; includes cations and anions.

Cation

Positively charged ion; electrons have been lost.

Anion

Negatively charged ion; electrons have been gained.

Valence electrons

Electrons in the outermost shell that determine bonding.

Electrolyte

Substance that ionizes in water and conducts electricity.

Free radical

Unstable molecule with an odd number of electrons; highly reactive.

Antioxidant

Chemical that neutralizes free radicals.

Molecule

Two or more atoms held together by chemical bonds.

Compound

A molecule with two or more different elements.

Isomer

Molecules with the same formula but different arrangement.

Molecular weight

Sum of the atomic weights of the atoms in a molecule.

Bond

Attractive force holding atoms together; can be ionic, covalent, hydrogen, or van der Waals.

Ionic bond

Attraction between oppositely charged ions; often dissociates in water.

Covalent bond

Bond formed by sharing electron pairs.

Nonpolar covalent

Equal sharing of electrons; no partial charges.

Polar covalent

Unequal sharing of electrons; results in partial charges.

Hydrogen bond

Weak attraction between a slightly positive H and a slightly negative atom (often O or N).

Van der Waals forces

Weak attractions between neutral atoms from transient electron distributions.

Water

Polar molecule; universal solvent; cohesive and adhesive; forms hydration spheres; high heat capacity.

Hydrophilic

Substances that dissolve in water; polar or charged.

Hydrophobic

Substances that do not dissolve in water; nonpolar.

Solution

Mixture with solute particles typically <1 nm; transparent; solute can pass through membranes.

Colloid

Mixture with 1–100 nm particles; cloudy; particles do not pass membranes.

Suspension

Mixture with >100 nm particles that tend to settle out.

Acid

Proton donor; releases H+ in water.

Base

Proton acceptor (or substance that releases OH− in water).

pH

Negative logarithm of hydrogen ion concentration.

Buffer

Substance that resists changes in pH.

Molarity

Moles of solute per liter of solution.

Milliequivalent per liter

Electrolyte concentration accounting for ion charge (mEq/L).

Metabolism

All chemical reactions in the body; includes catabolism and anabolism.

Catabolism

Energy-releasing breakdown of larger molecules.

Anabolism

Energy-using synthesis of larger molecules.

Exergonic

Reactions that release energy.

Endergonic

Reactions that require energy.

Oxidation

Loss of electrons; energy released; often involves oxygen.

Reduction

Gain of electrons; energy stored.

Redox

Coupled oxidation–reduction reactions.

Amino acid

Building block of proteins; contains amino and carboxyl groups and a variable R group.

Peptide bond

Covalent bond joining amino acids via dehydration synthesis.

Protein

Polymer of amino acids; 50+ amino acids; levels of structure from primary to quaternary; diverse functions.

Disulfide bridge

Covalent link between cysteine residues stabilizing protein structure.

Enzyme

Biological catalyst; typically a protein; speeds reactions (some ribozymes exist).

Active site

Region of an enzyme where the substrate binds.

Substrate

Molecule that binds to an enzyme's active site.

CoFactor

Nonprotein partner (inorganic ion) required for enzyme activity.

Coenzyme

Organic cofactor, usually vitamin-derived (e.g., NAD+).

Dehydration synthesis

Formation of a bond with removal of water; monomers → polymers.

Hydrolysis

Bond cleavage with addition of water; polymers → monomers.

Monomer

Small building block that can join to form polymers.

Polymer

Large molecule composed of repeating monomer units.