Chapter 2: The Chemistry of Life

Vocabulary-style flashcards covering core concepts from the lecture notes on the chemistry of life, including matter, atomic structure, bonds, chemical reactions, pH and buffers, and organic vs inorganic molecules.

Matter

Anything that has mass and takes up space.

Element

A fundamental substance that makes up matter and cannot be broken down by ordinary chemical means.

Major elements

Elements that account for about 99.9% of body mass; examples include N, C, H, O, P, S, Ca, K, Cl, Na, Mg; top four are O, C, H, and N.

Trace elements

Elements required in minute amounts (<0.01%) that often act as enzyme cofactors (e.g., Co, Cu, F, I, Fe, Mn, Zn).

Atom

The smallest unit of an element that retains the element’s properties.

Atomic number

The number of protons in an atom’s nucleus.

Atomic mass number

The sum of protons and neutrons in the nucleus.

Electron shells

Regions around the nucleus that hold electrons; first shell holds 2, second 8, third 8 electrons (for many elements).

Valence electrons

Electrons in the outermost shell involved in bonding.

Isotopes

Atoms of the same element with the same atomic number but different mass numbers due to different numbers of neutrons.

Radioisotope

An unstable isotope that decays and emits radiation; used in diagnosis and treatment.

Ion

An atom with a net electric charge from gain or loss of electrons; cation is positive, anion is negative.

Ionic bond

Bond formed when one atom loses and another gains electrons; typically between metals and nonmetals; bonds are relatively weak and common in nonliving substances.

Covalent bond

Bond formed when atoms share electrons; can be nonpolar (equal sharing) or polar (unequal sharing); strong bonds.

Hydrogen bond

Weak bond between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom; important for water properties and DNA structure.

Nonpolar covalent bond

Covalent bond where electrons are shared equally between atoms (e.g., H2).

Polar covalent bond

Covalent bond where electrons are shared unequally, creating partial charges (e.g., H2O).

Molecule

Two or more atoms bonded together.

Compound

Two or more atoms bonded together in which at least two different elements are present; proportions are fixed.

Mixture

Intermingling of two or more substances in varying proportions; includes suspensions, colloids, and solutions.

Suspension

Mixture in which solid particles are large and settle out (e.g., blood).

Colloid

Mixture with intermediate-sized particles that do not settle out (e.g., milk).

Solution

Homogeneous mixture where a solute is dissolved in a solvent; contains solutes and solvents.

Solvent

Substance in which solutes are dissolved (water is a common solvent).

Solute

Substance dissolved in a solvent.

Water

Polar solvent; most abundant compound in organisms; essential for transport, heat regulation, lubrication, and chemical reactions.

Dehydration synthesis

Chemical reaction that builds larger molecules by removing a molecule of water.

Hydrolysis

Chemical reaction that breaks bonds by adding water.

Acid

Substance that releases H+ ions in solution.

Base

Substance that releases OH− or accepts H+ in solution.

Salt

Product of an acid-base neutralization reaction; composed of cations and anions.

pH

Scale (0-14) measuring hydrogen ion concentration; 7 is neutral; below 7 is acidic; above 7 is basic.

Buffer

Substances that minimize changes in pH by neutralizing added acids or bases.

Activation energy

Minimum energy required to start a chemical reaction.

Enzyme

Protein catalysts that speed up reactions by lowering activation energy; substrate-specific; can be reused.

Substrate

Reactant that binds to an enzyme’s active site.

Active site

Region of the enzyme where the substrate binds.

Allosteric activator

Molecule that binds away from the active site to increase enzyme activity.

Allosteric inhibitor

Molecule that binds away from the active site to decrease enzyme activity.

Monosaccharide

A simple sugar; building block of carbohydrates; examples include glucose, fructose, galactose; hexoses.

Disaccharide

Two monosaccharides joined by a glycosidic bond; examples include sucrose, maltose, lactose.

Polysaccharide

Large carbohydrate formed by many monosaccharides; examples include starch, cellulose, glycogen.

Glycogen

Storage form of glucose in liver and muscles.

Lipids

Water-insoluble, energy-rich organic molecules (fats, oils, steroids) composed mainly of C, H, and O.

Triglyceride

Most common lipid; three fatty acids bound to glycerol; highly energy-dense and provides insulation.

Saturated fatty acid

Fatty acid chains fully hydrogenated with no double bonds; typically solid at room temperature.

Unsaturated fatty acid

Fatty acid chains with one or more double bonds; typically liquid at room temperature.

Phospholipid

Lipid with a glycerol backbone, two fatty acids, and a phosphate group; forms the lipid bilayer of cell membranes; hydrophilic head, hydrophobic tails.

Steroid

Lipids with four fused carbon rings; cholesterol is a steroid and precursor to hormones.

Cholesterol

Steroid important for cell membranes and a precursor to steroid hormones.

Protein

Most versatile organic molecule; functions include energy source, structure, hormones, and enzymes; built from amino acids.

Amino acid

Building block of proteins; contains an amino group, a carboxyl group, a hydrogen atom, and a distinctive side chain.

Peptide bond

Covalent bond linking amino acids in a protein chain.

Primary structure

A protein’s linear sequence of amino acids.

Secondary structure

Protein structure with coils or folds (alpha helices and beta sheets) formed by hydrogen bonds.

Tertiary structure

Overall three-dimensional folding of a single polypeptide.

Quaternary structure

Association of two or more polypeptide chains into a functional protein.

Denaturation

Loss of protein structure and function due to heat, pH changes, or chemicals.

Deamination

Removal of an amino group from an amino acid, enabling it to be used for energy or other biosynthetic purposes.

Nucleic acids

Large molecules that store and transfer genetic information; include DNA and RNA.

Nucleotide

Building block of nucleic acids; consists of a base, a phosphate group, and a five-carbon sugar.

RNA

Ribonucleic acid; single-stranded; ribose sugar; involved in protein synthesis.

DNA

Deoxyribonucleic acid; double-stranded; stores genetic code; deoxyribose sugar.

ATP

Adenosine triphosphate; the cell’s main energy currency.