Atoms, Molecules, and the Chemistry of Life

Vocabulary flashcards reviewing core biological and chemical concepts including atomic structure, chemical bonding, properties of water, macromolecule types, and protein/nucleic acid structure.

Element

A substance that cannot be broken down into simpler substances by ordinary chemical reactions.

Atom

The smallest unit of an element that retains that element's chemical properties.

Proton

A positively charged subatomic particle located within the atomic nucleus.

Neutron

An uncharged subatomic particle located within the atomic nucleus.

Electron

A negatively charged subatomic particle that rapidly orbits the atomic nucleus.

Atomic Number

The total number of protons in an atom, which defines the element and equals the number of electrons in an uncharged atom.

Atomic Mass

The sum of the mass of an atom's protons and neutrons, measured in atomic mass units (a.m.u.) or Daltons.

Molecule

A chemical structure consisting of two or more atoms held together by chemical bonds.

Organic Molecule

A molecule that contains a carbon-based backbone with $\text{C-C}$ and at least one $\text{C-H}$ bond.

Inorganic Molecule

A molecule that lacks carbon-based backbones and does not contain $\text{C-C}$ or $\text{C-H}$ bonds.

Valence Shell

The outermost electron shell of an atom, which dictates its chemical reactivity and bonding behavior.

Electronegativity

A measure of an atom's attraction or pulling force for shared electrons within a chemical bond.

Covalent Bond

A strong chemical bond formed when two atoms share electron pairs to fill their valence shells.

Non-polar Covalent Bond

A covalent bond in which shared electrons are distributed equally between the two involved atoms.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally due to electronegativity differences, resulting in partial positive and partial negative charges.

Ionic Bond

A strong bond resulting from the electrostatic attraction between oppositely charged ions formed by the full gain or loss of electrons.

Hydrogen Bond

A weak electrical attraction between a partially positive hydrogen atom in one polar molecule and a partially negative atom in another.

Cohesion

The attraction between water molecules created by hydrogen bonding, producing surface tension and pulling surface molecules downward.

Adhesion

The attraction between water molecules and other polar surfaces or substances.

Monomer

A small individual molecular subunit that bonds together with other subunits to form a polymer.

Polymer

A large molecule composed of many repeating monomer subunits linked together through chemical reactions.

Condensation Reaction

A dehydration reaction in which monomers polymerize, releasing a water molecule and requiring an input of energy.

Hydrolysis Reaction

A chemical reaction that breaks apart a polymer into monomers by consuming a water molecule and releasing energy.

Monosaccharide

The simple carbohydrate monomer unit consisting of a single sugar molecule, such as glucose, fructose, or galactose.

Polysaccharide

A complex carbohydrate polymer composed of many monosaccharide units linked together.

Glycogen

A short-term glucose storage polysaccharide formed in animals when immediate energy is not required.

Starch

A glucose storage polysaccharide found in plants.

Lipid

A hydrophobic, non-polar biological macromolecule that is greasy to the touch, does not dissolve in water, and provides significant energy storage.

Saturated Fat

A fat molecule in which each carbon in the hydrocarbon chain is single-bonded to two hydrogens, forming straight chains that pack tightly as solids at room temperature.

Unsaturated Fat

A fat molecule containing at least one carbon-carbon double bond ($\text{C}=\text{C}$), causing kinks in the chain that prevent tight packing and remain liquid at room temperature.

Phospholipid

A lipid composed of a hydrophilic head and two hydrophobic fatty acid tails, which assembles into bilayers that form cell membranes.

Primary Structure

The specific sequence of amino acids linked together in a polypeptide chain.

Secondary Structure

Corkscrew-like twists or pleated folds in a protein created by hydrogen bonds between amino acids in the polypeptide chain.

Tertiary Structure

The complex three-dimensional folded shape of a single polypeptide chain formed by interactions between side chains.

Quaternary Structure

The functional protein structure resulting from the combination and bonding of two or more distinct polypeptide chains.

Nucleotide

The structural monomer subunit of nucleic acids, consisting of a phosphate group, a 5-carbon sugar molecule, and a nitrogen-containing base.

Deoxyribonucleic Acid (DNA)

A double-stranded nucleic acid containing deoxyribose sugar that serves as a permanent genetic recipe book for protein synthesis.

Ribonucleic Acid (RNA)

A single-stranded nucleic acid containing ribose sugar and uracil that acts as a middleman molecule delivering instructions from DNA to direct protein synthesis.