Comprehensive Final-Exam Vocabulary Review

HONC

Mnemonic for the four most abundant elements in biomolecules: Hydrogen, Oxygen, Nitrogen, Carbon.

Electron

Sub-atomic particle with a ‑1 charge and ~0 amu located in orbitals around the nucleus.

Proton

Positively charged (+1) particle in the atomic nucleus; mass ≈ 1 amu.

Neutron

Electrically neutral particle in the nucleus; mass ≈ 1 amu.

Atomic Number

Number of protons in an atom; defines the element.

Mass Number

Total number of protons + neutrons in the nucleus.

Element

Substance whose atoms all have the same atomic number.

Isotope

Atoms of the same element with different mass numbers due to varying neutrons.

Alpha Particle

Helium-4 nucleus (2 p, 2 n) emitted during radioactive decay; low penetration.

Beta Particle

High-energy electron or positron emitted during nuclear decay.

Gamma Radiation

High-energy photons released from an excited nucleus; highly penetrating.

Bohr Model

Atomic model with electrons in fixed energy levels orbiting the nucleus.

Absorption (Bohr)

Electron gains energy and moves to a higher shell.

Excitation

State of an electron after absorbing energy to a higher orbital.

Relaxation

Electron’s return to a lower energy level, releasing energy.

Fluorescence

Emission of light as excited electrons relax to lower states.

Quantum Model

Modern atomic model describing electrons in probabilistic orbitals.

Orbital

3-D region where an electron is likely to be found.

Electron Shell

Principal energy level containing one or more subshells.

Subshell

Subdivision of a shell (s, p, d, f) containing orbitals.

Electron Configuration

Notation showing electron distribution among shells/subshells.

Periodicity

Recurring chemical trends across and down the periodic table.

Valence Shell

Outermost electron shell involved in bonding.

Octet Rule

Atoms gain/lose/share e⁻ to achieve eight valence electrons.

Lewis Dot Structure

Diagram showing valence electrons and bonding pairs.

Anion

Negatively charged ion formed by gaining electrons.

Cation

Positively charged ion formed by losing electrons.

Electronegativity

Atom’s tendency to attract shared electrons in a bond.

Non-polar Covalent Bond

Equal sharing of electrons; ΔEN ≈ 0–0.4.

Polar Covalent Bond

Unequal sharing of electrons; ΔEN ≈ 0.5–1.7.

Ionic Bond

Electrostatic attraction between oppositely charged ions.

Single Bond

One shared electron pair; longest, weakest covalent bond.

Double Bond

Two shared electron pairs; shorter and stronger than single.

Triple Bond

Three shared electron pairs; shortest, strongest covalent bond.

Chemical Equilibrium

Forward and reverse reaction rates are equal.

Equilibrium Constant (K)

Ratio of product/reactant concentrations at equilibrium.

Gibbs Free Energy (G)

Energy available to do work; ΔG predicts spontaneity.

Hydrogen Bond

Weak attraction between H in polar bond and electronegative atom.

Van der Waals Interaction

Weak transient attractions between fluctuating electron clouds.

Cohesion

Attraction between like water molecules via hydrogen bonding.

Adhesion

Attraction between water and other polar surfaces.

Calorie (cal)

Heat to raise 1 g water by 1 °C.

Percent Solution

g solute per 100 mL total solution.

Mole

6.022 × 10²³ particles of a substance.

Molarity (M)

Moles solute per liter of solution.

pH

-log[H⁺]; measures acidity.

Buffer

Weak acid/base pair that resists pH change.

Weak Acid

Partially dissociates in water, donating H⁺ weakly.

Conjugate Base

Species formed after an acid donates a proton.

Isomer

Compounds with same formula but different structures.

Structural Isomer

Differ in covalent arrangement of atoms.

Geometric Isomer

Differ around double bond (cis/trans).

Enantiomer

Mirror-image stereoisomers; chiral centers.

Diastereomer

Stereoisomers not mirror images.

Monomer

Single subunit of a polymer.

Polymer

Large molecule of repeating monomers.

Condensation Reaction

Builds polymers by removing H₂O (dehydration synthesis).

Hydrolysis

Breaks polymers by adding H₂O.

Functional Group

Specific atom cluster conferring chemical properties.

Monosaccharide

Single sugar unit (e.g., glucose).

Disaccharide

Two monosaccharides linked (e.g., sucrose).

Oligosaccharide

3–20 sugar units; often on cell surfaces.

Polysaccharide

Hundreds/thousands of monosaccharides (e.g., starch).

α 1-4 Linkage

Glycosidic bond forming helical starch chains.

α 1-6 Linkage

Branching glycosidic bond in glycogen.

β 1-4 Linkage

Straight linkage in cellulose fibers.

Saturated Fatty Acid

No C=C double bonds; solid at room temp.

Unsaturated Fatty Acid

One or more C=C; liquid at room temp.

Phospholipid

Glycerol + 2 fatty acids + phosphate head; forms bilayers.

Nucleotide

Sugar + phosphate + nitrogenous base monomer of nucleic acids.

Nucleic Acid

Polymer of nucleotides (DNA/RNA).

Phosphodiester Bond

Linkage between nucleotides’ phosphate and sugar.

DNA

Deoxyribonucleic acid; double-stranded hereditary polymer.

RNA

Ribonucleic acid; single-stranded, roles in gene expression.

Purine

Two-ring bases: adenine & guanine.

Pyrimidine

One-ring bases: cytosine, thymine, uracil.

Central Dogma

Information flow: DNA → RNA → Protein.

Amino Acid

Monomer with amino, carboxyl, R-group; builds proteins.

Peptide Bond

C-N bond linking amino acids.

Primary Structure

Linear amino-acid sequence of a protein.

Secondary Structure

α-helix or β-sheet stabilized by H-bonds.

Tertiary Structure

3-D folding of a single polypeptide.

Quaternary Structure

Assembly of multiple polypeptides.

Denaturation

Loss of protein structure (and function).

Plasma Membrane

Phospholipid bilayer with embedded proteins; selectively permeable.

FRAP

Fluorescence Recovery After Photobleaching; measures membrane fluidity.

Endomembrane System

ER, Golgi, lysosomes, vesicles, nuclear envelope, plasma membrane.

Peroxisome

Organelle catalyzing fatty-acid oxidation & H₂O₂ detoxification.

Mitochondrion

ATP-producing organelle via cellular respiration.

Chloroplast

Photosynthetic organelle containing thylakoids & stroma.

Microtubule

Tubulin polymers giving cell shape & chromosome movement.

Actin Filament

Thin filaments for cell motility & muscle contraction.

Intermediate Filament

Rope-like fibers providing tensile strength.

Prokaryote

Cell lacking a nucleus; Bacteria & Archaea.

Eukaryote

Cell with nucleus & membrane-bound organelles.

Gram-Positive

Thick peptidoglycan wall; purple Gram stain.

Gram-Negative

Thin wall + outer membrane; pink Gram stain.

Conjugation

DNA transfer via pilus between bacteria.

Transformation

Uptake of naked DNA from environment.

Transduction

DNA transfer by bacteriophages.