Chemical Level of Organization

Vocabulary flashcards covering the chemical level of organization, including atomic structure, chemical bonding, inorganic compounds, organic macromolecules, enzymes, and metabolism.

Matter

Anything that has mass and occupies space.

Element

The purest form of a substance that cannot be broken down into two or more substances, representing the fundamental materials that make up the human body.

Atom

The smallest unit of an element that retains the chemical properties of that element.

Proton

A positively charged subatomic particle ($p^+$) located within the nucleus of an atom.

Neutron

A neutral subatomic particle ($n^0$) located within the nucleus of an atom.

Electron

A negatively charged subatomic particle ($e^-$) that spins around the nucleus in electron shells or energy levels.

Atomic Number

The total number of protons in an atom's nucleus, which uniquely identifies an element.

Mass Number

The total number of protons plus neutrons in an atom's nucleus.

Valence Shell

An atom's outermost electron shell, which determines its chemical reactivity depending on how many electrons it contains.

Octet Rule

The chemical principle stating that an atom is stable when its outermost shell contains $8$ electrons, causing atoms to lose, gain, or share electrons to fill their valence shell.

Ion

An atom or group of atoms that carries a positive or negative electrical charge as a result of losing or gaining electrons.

Cation

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

Anion

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

Molecule

A chemical structure formed whenever two or more atoms link together by chemical bonds.

Compound

A molecule containing two or more atoms of different elements bound together by chemical bonds.

Isotope

A different form of an element whose atoms have the same number of protons but a different number of neutrons.

Ionic Bond

A chemical bond formed by the transfer of electrons from one atom to another, held together by strong electrostatic attraction between cations and anions.

Covalent Bond

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

Hydrogen Bond

A weak attraction between the weakly negative region of one polar molecule and the weakly positive region of another polar molecule.

Polar Molecule

A molecule that possesses unequal partial positive and negative charges due to unequal electron sharing in its covalent bonds.

Metabolism

The sum total of all biochemical reactions occurring in the body, consisting of anabolic and catabolic processes.

Anabolic Reaction

A metabolic reaction that forms chemical bonds to synthesize complex substances from simpler ones, requiring energy input.

Catabolic Reaction

A metabolic reaction that breaks chemical bonds in complex compounds to produce simpler molecules, releasing energy.

Synthesis Reaction

A chemical reaction in which two or more reactants combine to form a more complex product ($A + B \rightarrow AB$).

Decomposition Reaction

A chemical reaction in which bonds in a complex compound are broken down to yield simpler components ($AB \rightarrow A + B + \text{energy}$).

Exchange Reaction

A chemical reaction involving both decomposition and synthesis in which two reactants exchange components to produce two new products ($AB + CD \rightarrow AD + CB$).

Reversible Reaction

A chemical reaction that can proceed in both forward and reverse directions depending on conditions ($A + B \rightleftharpoons AB$).

Inorganic Compound

A chemical compound that lacks both carbon and hydrogen ($C-C$ or $C-H$) bonds, such as water, salts, acids, and bases.

Solution

A homogeneous liquid mixture consisting of a solvent that dissolves a solute completely.

Dehydration Synthesis

A chemical reaction that joins two molecules by forming a covalent bond while removing and releasing a molecule of water.

Hydrolysis

A chemical breakdown process in which a covalent bond between molecular subunits is cleaved by adding a molecule of water.

Salt

An inorganic compound formed by ionic bonding that dissociates into cations and anions when dissolved in water.

pH Scale

A measure of relative hydrogen ion ($H^+$) concentration ranging from $0$ (highly acidic) to $14$ (highly alkaline), with $7$ being neutral.

Acid

A substance that dissociates in solution to release hydrogen ions ($H^+$).

Base

A substance that releases hydroxide ions ($OH^-$) or accepts hydrogen ions ($H^+$) in solution.

Buffer

A chemical substance or biological system that maintains pH homeostasis by binding or releasing free hydrogen ions ($H^+$).

Organic Molecule

A compound composed of molecules containing carbon-carbon ($C-C$) or carbon-hydrogen ($C-H$) covalent bonds.

Monomer

A small molecular subunit that covalently links with other similar units to construct a macromolecule or polymer.

Monosaccharide

The monomer unit of carbohydrates, consisting of a single sugar molecule such as glucose, ribose, or deoxyribose.

Disaccharide

A carbohydrate formed by covalently bonding two monosaccharide units together, such as sucrose, lactose, or maltose.

Polysaccharide

A complex polymer carbohydrate formed from long chains of linked monosaccharide monomers, such as glycogen, starch, or cellulose.

Triglyceride

A lipid molecule composed of a glycerol backbone bound to three fatty acid tails.

Saturated Fatty Acid

A fatty acid chain containing no double bonds between carbon atoms and holding maximum hydrogen atoms, forming straight, rigid chains that are solid at room temperature.

Unsaturated Fatty Acid

A fatty acid chain containing one or more double bonds between carbon atoms, creating a kinked structure that remains liquid at room temperature.

Phospholipid

A structural lipid consisting of a glycerol backbone attached to a phosphate group (hydrophilic head) and two fatty acid tails (hydrophobic tails).

Steroid

A lipid molecule characterized by a core structure of four fused carbon rings, such as cholesterol.

Prostaglandin

A lipid-derived signaling molecule involved in regulating physiological responses and sensitizing nerve endings to pain.

Amino Acid

The structural monomer unit of proteins, structured with a central alpha carbon, an amino group ($NH_2$), a carboxyl group ($COOH$), a hydrogen atom, and a variable side chain ($R$).

Peptide Bond

A covalent bond formed via dehydration synthesis that connects amino acid monomers in a polypeptide chain.

Primary Structure

The specific linear sequence, number, and kind of amino acids constituting a polypeptide chain.

Secondary Structure

The local folding or coiling pattern of a polypeptide chain into an $\alpha$-helix or $\beta$-pleated sheet.

Tertiary Structure

The overall three-dimensional globular shape of a folded polypeptide, stabilized by hydrogen bonds, disulfide bonds, and other attractive forces.

Quaternary Structure

The functional protein structure resulting from the assembly and interaction of two or more folded polypeptide chains.

Denaturation

A process in which a protein loses its functional native three-dimensional shape due to heat, acids, bases, or chemical exposure.

Nucleotide

The monomer unit of nucleic acids, consisting of a pentose sugar, a nitrogen-containing base, and one or more phosphate groups.

Deoxyribonucleic Acid (DNA)

A double-stranded helical nucleic acid containing deoxyribose sugar and thymine that stores the genetic code for protein production.

Ribonucleic Acid (RNA)

A single-stranded nucleic acid containing ribose sugar and uracil that functions in translating genetic information into proteins.

Adenosine Triphosphate (ATP)

A high-energy nucleotide molecule composed of ribose, adenine, and three phosphate groups that acts as the primary energy currency of cells.

Enzyme

A functional protein that acts as a biological catalyst, speeding up chemical reactions by lowering activation energy without being consumed.

Activation Energy

The threshold amount of energy required to break chemical bonds and initiate a chemical reaction.

Enzyme-Substrate Complex

The temporary molecular structure formed when a reactant (substrate) binds to the active site of a specific enzyme.

Allosteric Effector

A molecule or factor that binds to an enzyme to alter its three-dimensional active site shape, thereby activating or inhibiting enzyme function.

Metabolic Pathway

A series of linked, enzyme-catalyzed chemical reactions in a cell where the product of one step acts as the substrate for the next.