Chapter 2: The Chemistry of Life Lecture Notes

Comprehensive vocabulary flashcards covering the basic chemistry, chemical bonds, reactions, and organic molecules relevant to Anatomy and Physiology.

Chemistry

The study of matter and its interactions.

Matter

Anything that has mass and occupies space; exists in three states: solid, liquid, or gas.

Atom

The smallest unit of matter that retains original properties; made up of subatomic particles.

Protons

Positively charged subatomic particles located in the central core of an atom (atomic nucleus).

Neutrons

Subatomic particles in the atomic nucleus that are slightly larger than protons and have no charge.

Electrons

Negatively charged subatomic particles located outside the atomic nucleus.

Atomic number

The number of protons in an atomic nucleus that defines every element.

Element

A substance that cannot be broken down into simpler substances by chemical means; made of atoms with the same number of protons.

Periodic table of elements

A table that lists elements by increasing atomic numbers, organized by groups with certain properties.

Metals

Shiny substances that conduct electricity, located on the left side of the periodic table red dividing line.

Nonmetals

Substances that exist as gases or brittle solids and are usually poor conductors of electricity, located on the right side of the periodic table red dividing line.

Mass number

Equal to the sum of all protons and neutrons in an atomic nucleus.

Isotope

An atom with the same atomic number (number of protons) but a different mass number (number of neutrons).

Radioisotopes

Unstable isotopes that release high energy or radiation through radioactive decay to assume a more stable form.

Radiotracers

Radioisotopes injected into a patient and detected by a camera to show the size, shape, and activity of organs and cells.

Suspension

A mixture containing two or more components with large, unevenly distributed particles that will settle out when left undisturbed.

Colloids

A mixture with small, evenly distributed particles that will not settle out due to interactions with surrounding molecules.

Solutions

A mixture with extremely small, evenly distributed particles that will not settle out; consists of a solute dissolved in a solvent.

Solute

The substance that is dissolved in a solution.

Solvent

The substance that dissolves the solute in a solution.

Molecule

A unit formed by chemical bonding between two or more atoms of the same element, such as $O_2$.

Compound

A unit formed when two or more atoms from different elements combine by chemical bonding, such as $H_2O$ or $C_6H_{12}O_6$.

Valence electrons

The electrons in the outermost shell of an atom that determine how an atom interacts and whether it will form bonds.

Octet rule

States that an atom is most stable when there are $8$ electrons in its valence shell.

Duet rule

States that an atom with $5$ or fewer electrons is most stable when its valence electron shell holds $2$ electrons.

Ionic bond

Formed when electrons are transferred from a metal atom to a nonmetal atom, resulting in the formation of ions.

Cation

A positively charged ion formed when a metal atom loses one or more electrons.

Anion

A negatively charged ion formed when a nonmetal atom gains one or more electrons.

Covalent bonds

The strongest type of chemical bond, formed when two or more nonmetals share electrons.

Electronegativity

The property of protons to attract electrons; highly electronegative elements strongly pull electrons away from less electronegative elements.

Nonpolar covalent bonds

Occur when two nonmetals in a molecule with similar or identical electronegativities pull with equal force and share electrons equally.

Polar covalent bonds

Occur when nonmetals with different electronegativities share electrons unequally, forming dipoles with partially positive and negative ends.

Hydrogen bonds

Weak attractions between the partially positive end of one dipole and the partially negative end of another dipole; responsible for surface tension in water.

Reactants

The starting ingredients on the left side of a chemical equation that undergo a reaction.

Products

The results of a chemical reaction, shown on the right side of a chemical equation.

Potential energy

Stored energy that can be released later to do work.

Kinetic energy

Energy set in motion to perform work; all atoms have this because they are in constant motion.

Chemical energy

The energy stored in the bonds between atoms; it drives nearly all chemical processes in the body.

Endergonic reactions

Chemical reactions that require an input of energy from another source; products contain more energy than reactants.

Exergonic reactions

Chemical reactions that release excess energy; products have less energy than reactants.

Homeostasis

The ability of an organism to maintain a stable internal environment despite changes in the external environment.

Catabolic reactions

Decomposition reactions where a large substance is broken down into smaller substances; usually exergonic as bonds are broken.

Anabolic reactions

Synthesis reactions where small simple subunits are united by chemical bonds to make large complex substances; these are endergonic.

Oxidation-reduction reactions (redox)

A special exchange reaction where electrons and energy are exchanged instead of atoms.

Oxidized

The reactant in a redox reaction that loses electrons.

Reduced

The reactant in a redox reaction that gains electrons.

Activation energy ($E_a$)

The energy required for all chemical reactions to proceed by reaching transition states.

Catalyst

A substance that increases the reaction rate by lowering activation energy without being consumed or altered itself.

Enzymes

Biological catalysts, mostly proteins, that speed up reactions by lowering activation energy and are highly specific for individual substrates.

Induced-fit mechanism

The process where the binding of a substrate causes a small shape change in the enzyme, bringing the substrate to its transition state.

Inorganic compounds

Compounds that generally do not contain carbon bonded to hydrogen; examples include water, acids, bases, and salts.

Organic compounds

Compounds that do contain carbon bonded to hydrogen.

Hydrophilic

Describes solutes with fully or partially charged ends that are able to dissolve in water.

Hydrophobic

Describes uncharged nonpolar covalent molecules, such as oils and fats, that do not dissolve in water.

Acid

A hydrogen ion or proton donor that increases the number of hydrogen ions in water.

Base (alkali)

A hydrogen ion acceptor that decreases the number of hydrogen ions in water.

pH scale

A scale ranging from $0-14$ representing the negative logarithm of the hydrogen ion concentration in a solution.

Buffer

A chemical system that resists changes in pH by preventing large swings when acid or base is added to a solution.

Electrolytes

Cations and anions formed when salts dissolve in water; they are capable of conducting an electrical current.

Monomers

Single subunits that are combined to build larger structures called polymers.

Dehydration synthesis

A reaction that links monomers together, resulting in the formation of a polymer and a molecule of water.

Hydrolysis

A catabolic reaction that uses water to break polymers into smaller monomer subunits.

Monosaccharides

Monomers from which all carbohydrates are made, containing $3$ to $7$ carbons; examples include glucose, fructose, and galactose.

Glycogen

The main storage polysaccharide of glucose in the body, found mostly in skeletal muscle and liver cells.

Lipids

A group of nonpolar hydrophobic molecules composed primarily of carbon and hydrogen, including fats and oils.

Saturated fatty acids

Fatty acids with no double bonds between carbon atoms that are solid at room temperature.

Triglyceride

A storage polymer for fatty acids consisting of three fatty acids linked to a glycerol backbone.

Phospholipids

Amphiphilic molecules consisting of a glycerol backbone, two fatty acid tails, and one phosphate head; central to cell membrane structure.

Steroids

Nonpolar lipids sharing a four-ring hydrocarbon structure known as the steroid nucleus.

Fibrous proteins

Proteins shaped like long rope-like strands composed of nonpolar amino acids that add strength and durability to structures.

Globular proteins

Spherical proteins composed mostly of polar amino acids that function as enzymes, hormones, and cell messengers.

Protein denaturation

The process of destroying a protein's shape and function through heat, pH changes, or chemical exposure.

Nucleotides

The monomers of nucleic acids, consisting of a nitrogenous base, a five-carbon pentose sugar, and a phosphate group.

Purines

Double-ringed nitrogenous bases, specifically adenine (A) and guanine (G).

Pyrimidines

Single-ringed nitrogenous bases, including cytosine (C), uracil (U), and thymine (T).

Adenosine triphosphate (ATP)

The main source of chemical energy in the body, composed of adenine, ribose, and three phosphate groups.

DNA (Deoxyribonucleic acid)

A double helix molecule containing genes that code for protein synthesis; contains the sugar deoxyribose and bases A, G, C, and T.

RNA (Ribonucleic acid)

A single strand of nucleotides that contains the sugar ribose and the base uracil instead of thymine; critical for making proteins.