Chapter 2: The Chemistry of Life

Vocabulary flashcards covering the key terms, chemical properties, biological molecules, and reaction mechanisms from Chapter 2 of Human Anatomy & Physiology I.

Minerals

Inorganic elements extracted from soil by plants and passed up the food chain to humans, constituting about 4% of human body weight and playing key roles in bone structure, enzyme function, and nerve/muscle cellular activities.

Nucleus (Atomic)

The dense center of an atom, composed of positively charged protons ($p^+$) and uncharged neutrons ($n^0$).

Valence Electrons

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

Ion

A charged particle (atom or molecule) that has an unequal number of protons and electrons.

Ionization

The process of transferring electrons from one atom to another.

Salts

Electrically neutral compounds formed by cations and anions that readily dissociate in water into individual ions and act as electrolytes.

Electrolytes

Substances that ionize in water and form solutions capable of conducting an electric current.

Free Radicals

Unstable, highly reactive particles possessing an unusual number of electrons, produced by metabolic reactions, radiation, or chemicals.

Antioxidants

Chemicals obtained through the diet (such as selenium, vitamin E, vitamin C, and carotenoids) that neutralize free radicals to prevent molecular damage.

Molecule

A particle composed of two or more atoms united by a chemical bond.

Compound

A molecule composed of two or more different chemical elements.

Isomers

Molecules that share the same molecular formula but have different structural arrangements of their atoms.

Ionic Bond

A chemical bond resulting from the electrostatic attraction between a cation and an anion.

Covalent Bond

A chemical bond formed when two atoms share one or more pairs of electrons.

Nonpolar Covalent Bond

A covalent bond in which shared electrons are attracted equally to both nuclei.

Polar Covalent Bond

A covalent bond in which shared electrons spend more time around one nucleus than another, giving that region a slight negative charge.

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.

Solvency

The ability of a liquid to dissolve other chemical substances.

Hydrophilic

Substances that are polarized or charged and readily dissolve in water.

Hydrophobic

Substances that are nonpolar or neutral and do not dissolve in water.

Adhesion

The physical tendency of one substance to cling to a different substance.

Cohesion

The physical tendency of molecules of the same substance to cling to each other.

Calorie (cal)

The base unit of heat, defined as the amount of heat needed to raise the temperature of $1\,g$ of water by $1^\circ\text{C}$.

Solution

A mixture of solute particles under $1\,nm$ in size dissolved in a solvent, which does not scatter light, passes through membranes, and will not separate on standing.

Colloid

A mixture with particles ranging from $1\text{--}100\,nm$ in size that scatter light, appear cloudy, and remain permanently mixed.

Suspension

A mixture containing particles larger than $100\,nm$ that render it cloudy or opaque and separate upon standing.

Emulsion

A suspension of one liquid in another liquid.

Acid

A proton donor that releases $H^+$ ions in water.

Base

A proton acceptor that accepts $H^+$ ions or releases $OH^-$ ions in water.

Buffers

Chemical solutions that resist changes in pH.

Molarity (M)

A measure of concentration expressed as the number of moles of solute per liter of solution.

Potential Energy

Energy stored in an object or system that is not currently performing work.

Kinetic Energy

Energy of motion, representing energy that is actively doing work.

Decomposition Reaction

A chemical reaction in which a large molecule breaks down into two or more smaller ones ($AB \rightarrow A + B$).

Synthesis Reaction

A chemical reaction in which two or more smaller molecules combine to form a larger one ($A + B \rightarrow AB$).

Exchange Reaction

A chemical reaction in which two molecules exchange atoms or groups of atoms ($AB + CD \rightarrow AC + BD$).

Metabolism

The sum of all chemical reactions occurring within the body.

Catabolism

Energy-releasing decomposition reactions within the body.

Anabolism

Energy-storing synthesis reactions within the body.

Oxidation

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

Reduction

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

Polymers

Large molecules made of a repetitive series of identical or similar subunits called monomers.

Dehydration Synthesis

A chemical reaction that joins monomers together by removing a hydroxyl group ($-OH$) from one and a hydrogen ($-H$) from another, producing water as a byproduct.

Hydrolysis

A chemical reaction that breaks down a polymer into monomers through the addition of a water molecule.

Monosaccharides

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

Disaccharides

Carbohydrates composed of two covalently bonded monosaccharides, such as sucrose, lactose, and maltose.

Polysaccharides

Long chains of monosaccharides (~50 or more), such as glycogen, starch, and cellulose.

Saturated Fatty Acid

A fatty acid chain in which carbon atoms are linked exclusively by single covalent bonds, holding as much hydrogen as possible.

Unsaturated Fatty Acid

A fatty acid chain that contains one or more double bonds between carbon atoms.

Phospholipids

Amphipathic lipids consisting of a hydrophilic phosphate head and two hydrophobic fatty acid tails, serving as the structural foundation of cell membranes.

Steroids

Lipids characterized by 17 carbon atoms arranged in four rings, synthesized from cholesterol.

Denaturation

An extreme conformational change in a protein caused by factors such as heat or pH that permanently destroys its biological function.

Primary Structure (Protein)

The sequence of amino acids joined by peptide bonds, encoded directly by genes.

Secondary Structure (Protein)

Coiled or folded shapes (such as an alpha helix or beta sheet) held together by hydrogen bonds.

Tertiary Structure (Protein)

The overall three-dimensional shape of a single polypeptide chain folded due to interactions among R groups and surrounding water.

Quaternary Structure (Protein)

The structural level resulting from the association of two or more individual polypeptide chains.

Enzymes

Proteins that function as biological catalysts to speed up chemical reactions by lowering activation energy.

Active Site

The specific pocket on an enzyme where substrate molecules bind.

Cofactor

A nonprotein partner (either an inorganic ion or an organic coenzyme) required by an enzyme to activate its catalytic function.

Phosphorylation

The enzymatic addition of a free phosphate group (released from ATP) to another molecule to activate it, carried out by kinases.

Glycolysis

The initial stage of glucose oxidation that splits glucose into two pyruvate molecules.

Nucleic Acids

Polymers composed of nucleotides (containing a phosphate group, pentose sugar, and nitrogenous base), including DNA and RNA.