Chemistry of Life Unit Study Guide

Comprehensive vocabulary flashcards covering the chemical elements, chemical bonding, water chemistry, acids/bases, and the four major biomolecules (carbohydrates, lipids, proteins, and nucleic acids) based on the unit lecture study guide.

Matter

Anything that takes up space and has mass, existing in three states: solid, liquid, and gas.

Element

A pure substance that cannot be broken down into simpler substances with different chemical or physical properties; all matter is composed of 92 naturally-occurring elements.

CHNOPS

The acronym representing the six chemical elements—carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—that make up $95\%$ of the body weight of organisms.

Atom

The smallest unit of an element that displays the properties of that element, composed of protons, neutrons, and electrons.

Atomic Number

The value that equals the number of protons and the number of electrons in an electrically neutral atom of an element.

Mass Number

The total sum of protons and neutrons contained in the nucleus of an atom.

Octet Rule

The rule stating that the innermost electron shell of an atom is complete with 2 electrons, while all subsequent outer shells require 8 electrons to be complete and stable.

Valence Shell

The outermost electron shell of an atom that determines its chemical properties and capacity to give up, accept, or share electrons.

Molecule

A chemical unit formed when atoms of two or more elements bond together; the smallest part of a compound that retains its properties.

Compound

A molecule that contains atoms of at least two different elements bonded together (e.g., $H_2O$).

Ionic Bond

A chemical bond formed when electrons are completely transferred from one atom to another, resulting in oppositely charged ions held together by electrostatic attraction.

Covalent Bond

A chemical bond formed when two atoms share pairs of electrons to achieve a stable outer shell.

Nonpolar Covalent Bond

A covalent bond characterized by the equal sharing of electrons between atoms, where the electrons are not attracted to either atom to a greater degree.

Polar Covalent Bond

A covalent bond resulting from unequal sharing of electrons due to differences in the electronegativity of the participating atoms.

Electronegativity

The relative attraction of an atom for electrons shared within a covalent bond.

Hydrogen Bond

A weak attractive force between the slightly positive hydrogen atom of one molecule and a slightly negative atom (such as oxygen or nitrogen) in another or the same molecule.

Calorie

The amount of heat energy required to raise the temperature of one gram of water by $1^\circ\text{C}$.

Hydrophilic

Describing ionized or polar molecules that are attracted to water and readily dissolve in it ("water loving").

Hydrophobic

Describing nonionized and nonpolar molecules that cannot attract water and do not dissolve in it ("water fearing").

Cohesion

The property of water molecules to cling to one another via hydrogen bonding, allowing water to flow freely without separating.

Adhesion

The ability of water molecules to cling to external polar surfaces due to their polarity.

Capillary Action

The upward movement of water through narrow tubes (such as from roots to leaves in plants) driven by the combined effects of adhesion and cohesion.

Surface Tension

The cohesive force at the surface of a liquid that makes it relatively difficult to break through, enabling objects like rocks to skip or insects to walk across pond surfaces.

Acid

A substance that dissociates in water and releases hydrogen ions ($H^+$), possessing a pH value less than 7.

Base

A substance that takes up hydrogen ions ($H^+$) or releases hydroxide ions ($OH^-$), possessing a pH value greater than 7.

pH Scale

A logarithmic measurement scale ranging from 0 to 14 that indicates the acidity or basicity of a solution based on the negative logarithm of the hydrogen ion concentration ($-\log[H^+]$).

Buffer

A chemical or combination of chemicals that stabilizes the pH of a solution by taking up excess hydrogen ions ($H^+$) or hydroxide ions ($OH^-$).

Acid Deposition

Rain, snow, or dry particles falling from the atmosphere to Earth that possess a pH value less than 5.0, largely caused by the burning of fossil fuels.

Functional Groups

Specific clusters of atoms attached to a carbon skeleton that possess characteristic chemical structures and reactivities (such as hydroxyl or carboxyl groups).

Isomers

Molecules that possess identical molecular formulas but differ in the spatial arrangement of their atoms, giving them distinct chemical properties.

Dehydration Reaction

A chemical synthesis reaction that joins monomers into polymers by eliminating a molecule of water ($-\text{OH}$ from one monomer and $-\text{H}$ from the other).

Hydrolysis Reaction

A chemical reaction that breaks polymers down into smaller monomer units through the addition and splitting of a water molecule.

Monosaccharide

A simple sugar consisting of a single monomer with a carbon backbone of 3 to 7 carbons (e.g., glucose, fructose, galactose).

Disaccharide

A carbohydrate composed of two monosaccharides joined together by a dehydration reaction (e.g., maltose, sucrose, lactose).

Glycosidic Bond

The covalent linkage formed between two monosaccharides during a condensation/dehydration reaction.

Starch

A plant energy storage polysaccharide consisting of glucose polymers in unbranched helical forms (amylose) or branched forms (amylopectin).

Glycogen

A highly branched polysaccharide of glucose used by animals for short-term energy storage in liver and muscle cells.

Cellulose

A structural polysaccharide composed of glucose chains linked by $\beta\text{-1,4-glycosidic linkages}$ forming microfibrils in plant cell walls; indigestible to humans.

Chitin

A structural polysaccharide made of glucose derivatives with attached amino groups, forming the exoskeleton of arthropods and cell walls of fungi.

Peptidoglycan

A complex structural polysaccharide of glucose derivatives cross-linked by chains of amino acids, located in bacterial cell walls.

Fatty Acid

A lipid subunit consisting of a long hydrocarbon chain ending in a carboxylic acid group ($-\text{COOH}$).

Saturated Fatty Acid

A fatty acid that has no double bonds between carbon atoms in its hydrocarbon chain, is fully saturated with hydrogen, and is solid at room temperature.

Unsaturated Fatty Acid

A fatty acid that contains one or more double bonds in its hydrocarbon chain, causing kinks/bends and remaining liquid at room temperature.

Triglyceride

A neutral lipid molecule composed of a single glycerol molecule bonded to three fatty acids via ester bonds, used for long-term energy storage.

Phospholipid

An amphipathic membrane lipid consisting of a glycerol backbone bonded to two hydrophobic fatty acid tails and a polar, hydrophilic phosphate head group.

Steroid

A category of lipids defined by a carbon skeleton of four fused rings, functioning in membrane fluidity and serving as precursors for hormones.

Amino Acid

The monomer building block of proteins, featuring a central carbon atom bonded to a hydrogen atom, an amino group ($-\text{NH}_2$), a carboxyl group ($-\text{COOH}$), and a distinct R group.

Peptide Bond

The covalent linkage formed between the carboxyl carbon of one amino acid and the amino nitrogen of an adjacent amino acid via condensation.

Denaturation

The irreversible loss of a protein's natural three-dimensional shape and biological function due to disruption of its bonds by external factors such as high temperatures.

Nucleotide

The structural monomer of nucleic acids, composed of a pentose sugar, an inorganic phosphate group, and a nitrogenous base.

ATP (Adenosine Triphosphate)

A specialized high-energy nucleotide composed of ribose, adenine, and three phosphate groups, whose terminal phosphate hydrolysis powers cellular metabolic work.