Chapter 2: Chemistry of Life

Vocabulary flashcards covering key terms from the lecture notes on matter, mixtures, chemical bonds, water and acids/bases, inorganic and organic compounds, and major biomolecules (carbohydrates, lipids, proteins, and nucleic acids).

Chemical level

The most basic structural level of organization, consisting of atoms and molecules that make up living matter.

Atom

The smallest unit of matter that retains the properties of an element.

Element

A substance composed of one or more identical atoms; cannot be broken down into simpler substances by chemical means.

Proton (p+)

Positively charged subatomic particle located in the nucleus.

Neutron (n0)

Neutral subatomic particle located in the nucleus.

Electron (e-)

Negatively charged subatomic particle that surrounds the nucleus.

Electrically neutral

Having equal numbers of protons and electrons; no net electric charge.

Atomic number

The number of protons in the nucleus; defines the identity of the element.

Mass number

The total number of protons and neutrons in the nucleus.

Isotope

An atom with the same number of protons but a different number of neutrons.

Radioisotope

An unstable isotope that releases energy as radiation.

Ion

A charged atom formed when an atom gains or loses electrons.

Cation

A positively charged ion.

Anion

A negatively charged ion.

Electron shells (energy levels)

Regions around the nucleus where electrons are found; first shell holds 2, second 8, third up to 18.

Valence shell

Outermost electron shell of an atom.

Valence electrons

Electrons in the valence shell involved in bonding.

Octet rule

Atoms are most stable with 8 electrons in the valence shell.

Duet rule

Atoms with 5 or fewer electrons are most stable with 2 electrons in the first shell.

Ionic bond

A bond formed by transfer of electrons between atoms, creating oppositely charged ions that attract.

Covalent bond

A bond formed by sharing electron pairs between atoms; can be single, double, or triple.

Nonpolar covalent bond

Electrons are shared equally; typically between identical atoms or between carbon and hydrogen.

Polar covalent bond

Electrons are shared unequally, creating partial charges on the atoms.

Hydrogen bond

Weak attractions between partially positive hydrogen atoms and partially negative atoms in polar molecules.

Water

A vital solvent and medium for life; makes up ~50-65% of body mass and has unique properties like high heat capacity and lubrication.

Solvent

The dissolving medium in a solution (often water).

Solute

The substance dissolved in a solvent.

Hydrophilic

Solutes that dissolve in water; water-loving.

Hydrophobic

Solutes that do not dissolve in water; water-hating.

pH

A measure of hydrogen ion concentration in a solution; neutral is 7.

Acid

A substance that donates hydrogen ions (increases H+ in solution).

Base

A substance that accepts hydrogen ions (decreases H+ in solution).

Buffer

A system that helps maintain pH by neutralizing added acids or bases; maintains homeostasis.

Acidosis

Condition where blood pH falls below 7.35.

Alkalosis

Condition where blood pH rises above 7.45.

Salt

A compound consisting of a metal cation and a nonmetal anion held together by ionic bonds.

Electrolyte

Dissolved ions that conduct an electric current and are essential for body function.

Inorganic compounds

Compounds that do not contain carbon-hydrogen bonds.

Organic compounds

Compounds that contain carbon-hydrogen bonds.

Hydrocarbons

Organic compounds consisting only of carbon and hydrogen.

Monomer

A single subunit that can be joined to form polymers.

Polymer

A large molecule composed of many monomers linked together.

Dehydration synthesis

A chemical reaction that links two monomers with removal of a water molecule.

Hydrolysis

A chemical reaction that splits a polymer by adding a water molecule.

Carbohydrates

Compounds of C, H, and O; primary energy source; includes monosaccharides, disaccharides, and polysaccharides.

Monosaccharide

A single sugar unit (e.g., glucose, fructose, galactose, ribose, deoxyribose).

Glucose

The primary energy source for most cells.

Ribose

A five-carbon sugar found in RNA.

Deoxyribose

A five-carbon sugar found in DNA.

Disaccharide

A carbohydrate formed by two monosaccharides (e.g., sucrose, lactose, maltose).

Polysaccharide

A long chain of monosaccharides; mainly for energy storage (e.g., starch, glycogen).

Lipids

Molecules rich in carbon and hydrogen; include fats, phospholipids, and steroids; primarily energy storage and membranes.

Fatty acids

Hydrocarbon chains with a carboxyl group; building blocks of lipids.

Saturated fatty acid

Fatty acid with no double bonds between carbons; typically solid at room temperature.

Monounsaturated fatty acid

Fatty acid with one double bond; typically liquid at room temperature.

Polyunsaturated fatty acid

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

Triglycerides

Three fatty acids linked to a glycerol backbone; main form of stored fat.

Phospholipids

Two fatty acids and a phosphate group attached to glycerol; major component of cell membranes.

Steroids

Lipids with a four-ring structure; include cholesterol and steroid hormones.

Cholesterol

A steroid that serves as a precursor for other steroids and helps form cell membranes.

Proteins

Macromolecules made of amino acids; essential for catalysis, structure, signaling, and function.

Amino acids

Monomers of proteins; there are 21 types used to build proteins.

Peptides

Short chains of amino acids; dipeptides, tripeptides, and polypeptides.

Fibrous protein

Proteins with elongated shape; provide structural support (e.g., collagen, keratin).

Globular protein

Globular-shaped proteins; include many enzymes and hormones.

Protein denaturation

Loss of a protein’s native shape and function due to heat, pH, or chemicals.

Nucleic acids

DNA and RNA; store and transmit genetic information; composed of nucleotides.

Nucleotides

Monomers of nucleic acids.

DNA

Deoxyribonucleic acid; stores genetic information in a double helix.

RNA

Ribonucleic acid; conveys genetic instructions and helps synthesize proteins.

ATP

Adenosine triphosphate; the primary energy currency of the cell; produced mainly from glucose; depleted in 60–90 seconds without replenishment.

Gene

Segment of DNA that contains the information to make one protein.

Activation energy

Energy required to start a chemical reaction by allowing reactant particles to collide effectively.

Exergonic reaction

A reaction that releases energy to the surroundings.

Endergonic reaction

A reaction that absorbs energy from the surroundings.

Catabolic reactions

Reactions that break down larger substances into smaller ones.

Anabolic reactions

Reactions that build larger molecules from smaller ones.

Exchange reactions

Reactions involving the transfer or exchange of atoms or electrons between reactants.

Enzymes

Biological catalysts that speed up reactions by lowering activation energy; highly specific and not consumed.

Substrate

The reactant(s) that bind to an enzyme.

Macromolecules

Very large biological molecules such as carbohydrates, proteins, nucleic acids, and lipids.