Chapter 2: Chemistry of Life

Vocabulary flashcards generated from Human Biology Chapter 2, covering atomic structure, chemical bonding, properties of water, pH and buffers, and the four major classes of biological macromolecules.

Matter

Anything that takes up space and has mass, existing in solid, liquid, gaseous, or plasma forms.

Element

A pure substance considered a building block of matter that cannot be broken down by chemical reactions.

Atom

The basic unit of matter that makes up an element, consisting of a central nucleus surrounded by electron energy shells.

Proton

A positively charged subatomic particle located in the central nucleus of an atom.

Neutron

A subatomic particle with no electrical charge located in the central nucleus of an atom.

Electron

A negatively charged subatomic particle that orbits the nucleus of an atom in energy shells.

Atomic Number

The number of protons in an atom, which uniquely determines the identity of an element.

Atomic Mass

The mass of an element, roughly equal to the sum of its protons and neutrons.

Isotope

Atoms of the same element that have the same atomic number but different mass numbers due to having more neutrons.

Radioisotope

An unstable isotope that emits energy called radiation.

Molecule

A group of two or more atoms bonded together, which can be composed of the same or different elements.

Compound

A molecule specifically composed of two or more different types of atoms.

Covalent Bond

A chemical bond formed when atoms share a pair of electrons to attain a stable outer electron shell.

Ionic Bond

A chemical bond formed by the electrostatic interaction between a positively charged ion (cation) and a negatively charged ion (anion).

Hydrogen Bond

An attraction between oppositely charged regions of polar molecules.

High Heat Capacity

The property of water that allows it to resist changes in temperature by absorbing and releasing heat through hydrogen bonds.

High Heat of Vaporization

The property of water requiring significant energy to break hydrogen bonds in order to evaporate from liquid to gas.

Cohesion

The tendency of water molecules to hold together with each other through hydrogen bonding.

Adhesion

The attraction between water molecules and a different surface or substance, such as plant cell walls.

pH Scale

A scale ranging from $0$ to $14$ that measures the concentration of $\text{H}^+$ ions in a solution to determine its acidity or basicity.

Buffer

A solution that resists changes in $\text{pH}$ when acids or bases are added by absorbing or releasing $\text{H}^+$ ions.

Monomer

A small subunit or building block molecule that covalently bonds with similar units to form a polymer.

Polymer

A large macromolecule composed of multiple repeating monomer units linked together by covalent bonds.

Monosaccharide

A single sugar molecule, such as glucose, fructose, or galactose, serving as a basic building block of carbohydrates.

Disaccharide

A carbohydrate formed by joining two monosaccharide molecules together, such as sucrose, lactose, or maltose.

Polysaccharide

A complex carbohydrate composed of long chains of monosaccharides linked together, such as starch or glycogen.

Glycogen

A polysaccharide composed of branched chains of glucose that serves as accessible short-term energy storage in animals.

Cellulose

A structural polysaccharide found in plant cell walls, commonly known as fiber, which cannot be digested by human enzymes.

Triglycerides

Lipids composed of one glycerol molecule attached to three fatty acid chains, commonly existing as fats or oils.

Saturated Fats

Triglycerides that are solid at room temperature, contain no double bonds in their fatty acid chains, and raise low-density lipoprotein ($\text{LDL}$) levels.

Unsaturated Fats

Triglycerides that are liquid at room temperature, contain one or more double bonds in their fatty acid chains, and raise high-density lipoprotein ($\text{HDL}$) levels.

Trans Fats

Unnatural fatty acids produced by hydrogenation reactions that significantly increase the risk of heart disease.

Phospholipid

A lipid consisting of a hydrophilic polar head and two hydrophobic non-polar tails, serving as the main structural component of cell membranes.

Steroids

Lipids characterized by a structure of four fused carbon rings, including molecules such as cholesterol and sex hormones.

Low-Density Lipoprotein (LDL)

A lipoprotein that delivers fat to cells, high levels of which are associated with increased cardiovascular risk.

High-Density Lipoprotein (HDL)

A lipoprotein that removes fat from the bloodstream for excretion, commonly considered beneficial for cardiovascular health.

Amino Acid

The monomer building block of proteins, consisting of a central carbon bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R group.

Primary Structure

The unique linear sequence of amino acids in a polypeptide chain held together by covalent peptide bonds.

Secondary Structure

The folding or coiling of a polypeptide chain into structures like $\alpha$-helices or $\beta$-pleated sheets maintained by hydrogen bonds.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide chain formed by non-covalent interactions between R groups.

Quaternary Structure

The protein structure formed when two or more polypeptide chains bond together into a single functional complex.

Nucleotide

The monomer building block of nucleic acids, consisting of a phosphate group, a 5-carbon sugar, and a nitrogenous base.

Deoxyribonucleic Acid (DNA)

A double-stranded nucleic acid containing deoxyribose sugar that stores genetic instructions for making $\text{RNA}$ and proteins.

Ribonucleic Acid (RNA)

A single-stranded nucleic acid containing ribose sugar that translates genetic instructions from $\text{DNA}$ to produce proteins.

Adenosine Triphosphate (ATP)

A high-energy nucleotide containing three phosphate groups that serves as the primary energy carrier in cells.