A/P Chapter 2 The Chemistry of Life

Chemical element

The simplest form of matter to have unique chemical properties.

Atomic number

The unique identifier of an element determined by the number of protons in its nucleus.

Major elements of the body

The six elements that account for 98.5% of the body's weight: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

Lesser elements of the body

The six elements that make up 0.8% of the body's weight: sulfur, potassium, sodium, chlorine, magnesium, and iron.

Trace elements

The 12 elements that make up a minute fraction (0.7%) of the body's total weight but play vital physiological roles.

Minerals

Inorganic elements extracted from the soil by plants and passed up the food chain; they constitute 4% of the body's weight and contribute to structures (like teeth and bones) and enzyme functions.

Proton

A subatomic particle located in the nucleus with a positive electrical charge and a mass of 1 amu.

Neutron

A subatomic particle located in the nucleus with no electrical charge and a mass of 1 amu.

Electron

A subatomic particle with a negative charge that orbits the nucleus in concentric clouds or shells.

Atomic mass

The total number of protons and neutrons within the nucleus of an atom.

Valence electrons

The electrons located in the outermost shell of an atom that determine its chemical bonding properties.

Isotopes

Varieties of an element that differ from one another only in the number of neutrons contained in the nucleus.

Radioisotopes

Unstable isotopes that decay over time into stable isotopes while releasing radiation.

Physical half-life

The specific amount of time required for exactly 50% of a radioisotope's atoms to decay.

Biological half-life

The time required for half of a radioactive substance to be cleared and eliminated from the body by physiological processes.

Ions

Charged particles with unequal numbers of protons and electrons.

Anion

A particle that has gained one or more electrons, giving it a net negative electrical charge.

Cation

A particle that has lost one or more electrons, giving it a net positive electrical charge.

Electrolytes

Mineral salts that ionize in water and form solutions capable of conducting electricity, vital for nerve and muscle function.

Free radicals

Unstable, highly reactive chemical particles with an odd number of electrons that can damage body tissues.

Antioxidants

Chemicals that neutralize free radicals, helping to defend body cells from oxidative damage.

Molecules

Chemical particles composed of two or more atoms united by a chemical bond.

Compounds

Molecules composed of two or more different chemical elements.

Molecular weight

The sum of the atomic masses of all the atoms in a molecule.

Ionic bond

A chemical bond formed by the electrostatic attraction between a cation and an anion.

Covalent bond

A chemical bond formed by the sharing of one or more pairs of electrons between two nuclei.

Single covalent bond

The sharing of a single pair of electrons between two atoms.

Double covalent bond

The sharing of two pairs of electrons between two atoms.

Nonpolar covalent bond

A covalent bond in which the shared electrons spend an equal amount of time around each nucleus; the strongest type of chemical bond.

Polar covalent bond

A covalent bond in which the shared electrons spend more time orbiting one nucleus than the other, creating partial negative and positive regions.

Hydrogen bond

A weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another molecule.

Van der Waals forces

Weak, brief attractions between neutral atoms caused by random fluctuations in electron density.

Mixture

A substance consisting of chemicals that are physically blended together but not chemically combined.

Hydrophilic

Substances that dissolve readily in water, such as sugar or salt (water-loving).

Hydrophobic

Substances that do not dissolve in water, such as fats and oils (water-fearing).

Adhesion

The tendency of one substance to cling to another, such as water clinging to body tissues.

Cohesion

The tendency of molecules of the same substance to cling to each other, creating surface tension.

Chemical reactivity

The ability of water to participate in chemical equations, such as ionizaton, hydrolysis, and dehydration synthesis.

Thermal stability

The property of water requiring high amounts of heat to change its temperature, helping stabilize internal body temperature.

Solute

The matter that is dissolved into a solution, consisting of small particles that do not scatter light or settle.

Solvent

The liquid medium that dissolves a solute, most commonly water in living systems.

Solution

A clear mixture of a solute and solvent where the particles do not separate when left standing.

Colloid

A mixture consisting of larger particles (1 to 100 nm) that scatter light but do not settle out, such as gelatin or albumin in blood plasma.

Suspension

A mixture containing large particles (exceeding 100 nm) that render it cloudy and settle out over time, such as blood cells suspended in plasma.

Emulsion

A suspension of one liquid in another, such as oil and water or fat ribbons in breast milk.

Acid

A proton donor; a chemical substance that releases hydrogen ions (H+) in a solution.

Base

A proton acceptor; a chemical substance that binds to hydrogen ions or releases hydroxide ions (OH-).

pH scale

A logarithmic measurement scale from 0 to 14 indicating the molar concentration of hydrogen ions in a solution.

Buffer

A chemical solution or mechanism that resists changes in pH by converting strong acids or bases into weaker ones.

Weight per volume

A measure of concentration expressing the weight of solute in a given volume of solution (e.g., mg/dL).

Percentages

A concentration measurement expressing the weight of solute per 100 mL of solution.

Molarity

A concentration measurement expressing the number of moles of solute per liter of solution, reflecting the actual number of molecules present.

Work

The movement of matter or the modification of its structure; all physiological activities are forms of work.

Energy

The capacity to do work.

Potential energy

Energy contained within an object because of its position or internal chemical configuration, but not actively doing work.

Kinetic energy

The energy of motion; energy that is actively doing work or moving matter.

Chemical energy

A form of potential energy stored within the covalent bonds of chemical molecules.

Free energy

The potential energy available in a chemical system to do useful work.

Chemical reaction

A process in which a covalent or ionic bond is formed or broken apart.

Chemical equation

A written symbolic representation of a chemical reaction showing reactants on the left and products on the right.

Decomposition reaction

A reaction where a large molecule breaks down into two or more smaller fragments.

Synthesis reaction

A reaction where two or more small molecules combine to build a larger, more complex molecule.

Exchange reaction

A chemical reaction where two molecules collide and trade atoms or groups of atoms.

Reversible reactions

Reactions that can proceed in either direction depending on the relative abundance of reactants and products.

Law of mass action

The principle that reversible reactions proceed from the side with greater concentration to the side with lesser concentration.

Catalysts

Substances that temporarily bind to reactants to hold them in a favorable orientation, speeding up a reaction without being consumed.

Metabolism

The sum total of all chemical reactions occurring inside an organism.

Anabolism

The metabolic subcategory of energy-storing synthesis reactions, such as building protein or fat.

Catabolism

The metabolic subcategory of energy-releasing decomposition reactions that break down covalent bonds.

Oxidation

A chemical reaction in which a molecule gives up electrons and releases chemical energy.

Reduction

A chemical reaction in which a molecule gains electrons and absorbs chemical energy.

Organic chemistry

The study of compounds containing carbon backbones.

Functional groups

Groups of atoms attached to a carbon backbone that determine the specific chemical properties of an organic molecule.

Monomers

The basic chemical subunits that link together to construct large macromolecules.

Polymers

Molecules made up of a repetitive series of identical or similar monomers.

Dehydration synthesis

A chemical process that joins monomers into polymers by removing a water molecule.

Hydrolysis

A chemical process that breaks a polymer down into monomers by splitting and inserting a water molecule.

Carbohydrates

Hydrophilic organic molecules with the general formula (CH2O)n, serving primarily as a source of cellular energy.

Monosaccharides

The simplest carbohydrate monomers, including glucose, fructose, and galactose.

Disaccharides

Carbohydrates composed of two monosaccharides joined together, including sucrose, lactose, and maltose.

Polysaccharides

Long polymers of monosaccharides, such as glycogen (stored in animals), starch (stored in plants), and cellulose.

Glycolipids

Carbohydrates covalently bonded to lipids, found on the external surface of the plasma membrane.

Glycoproteins

Carbohydrates covalently bonded to proteins, forming a major component of mucus and membrane structures.

Proteoglycans

Macromolecules dominated by carbohydrates with a smaller protein component, acting as a structural filler in tissues and lubricants in joints.

Lipids

Hydrophobic organic molecules with a high ratio of hydrogen to oxygen, including fatty acids, triglycerides, phospholipids, and steroids.

Fatty acid

A linear chain of carbon atoms with a carboxyl group at one end and a methyl group at the other.

Saturated fatty acid

A fatty acid containing as much hydrogen as possible, with no double bonds between carbon atoms.

Unsaturated fatty acid

A fatty acid containing one or more double bonds along its carbon chain, leaving empty slots where hydrogens could bind.

Triglycerides

Lipids consisting of three fatty acids linked to a single glycerol molecule; used for energy storage, insulation, and cushioning.

Phospholipids

Amphipathic lipids containing two fatty acid tails (hydrophobic) and a phosphate head (hydrophilic), forming the structural backbone of membranes.

Eicosanoids

20-carbon fatty acid derivatives that act as powerful hormone-like chemical messengers among cells (e.g., prostaglandins).

Steroid

A lipid featuring a core structure of four interconnected carbon rings, with cholesterol serving as the parent compound.

Protein

A polymer composed of amino acid monomers linked together by peptide bonds.

Amino acid

The structural subunit of a protein, consisting of a central carbon, an amino group, a carboxyl group, and a variable radical (R) group.

Peptide bond

The covalent bond formed by dehydration synthesis that links the amino group of one amino acid to the carboxyl group of another.

Primary structure

The specific, linear sequence of amino acids making up a protein chain.

Secondary structure

The coiled or folded shape of a protein chain (alpha helix or beta pleated sheet) held together by hydrogen bonds.

Tertiary structure

The complex, three-dimensional folding of a protein chain caused by hydrophobic interactions and disulfide bridges.

Quaternary structure

The functional association of two or more separate polypeptide chains working together as a single protein complex (e.g., hemoglobin).

Denaturation

A drastic, sometimes permanent change in the three-dimensional shape of a protein caused by extreme heat or pH, destroying its biological function.