BIOLOGY 1103 – Atoms, Molecules & Biochemistry

Vocabulary flashcards covering key terms about atoms, molecules, water, and macromolecules from Biology 1103 lecture notes.

Chemical Element

A pure substance that cannot be broken down chemically into other substances; identified by a name and symbol (e.g., H, C, O, N).

Atom

Smallest unit of an element that retains that element’s chemical properties; composed of protons, neutrons, and electrons.

Subatomic Particle

Particles that make up atoms: protons (positive), neutrons (neutral), and electrons (negative).

Proton

Positively charged subatomic particle located in the atomic nucleus; determines the element’s identity.

Neutron

Neutral subatomic particle in the nucleus; adds mass and may vary among isotopes.

Electron

Negatively charged subatomic particle that orbits the nucleus in shells; determines chemical behavior.

Isotope

Atoms of the same element with different numbers of neutrons; chemically identical but differ in mass.

Electron Shell

Energy level where electrons are found; first holds 2 electrons, second 8, third up to 18.

Valence Shell

Outermost electron shell of an atom; its electron count dictates reactivity.

Valence Electron

Electron found in the valence shell involved in bonding.

Molecule

Two or more atoms bonded together (e.g., O2, H2O).

Compound

A molecule consisting of two or more different elements (e.g., H2O, CO2).

Ion

Atom or molecule with an electrical charge due to gain or loss of electrons.

Cation

Positively charged ion formed by electron loss (e.g., Na⁺).

Anion

Negatively charged ion formed by electron gain (e.g., Cl⁻).

Ionic Bond

Electrostatic attraction between oppositely charged ions (e.g., NaCl).

Covalent Bond

Strong bond formed when two atoms share pairs of electrons.

Non-polar Covalent Bond

Covalent bond with equal electron sharing; no charge separation (e.g., O2).

Polar Covalent Bond

Covalent bond with unequal electron sharing, creating partial charges (e.g., H2O).

Electronegativity

An atom’s attraction for shared electrons; higher electronegativity pulls electrons closer.

Organic Molecule

Molecule containing carbon with C–H covalent bonds; usually large and energy-rich (e.g., glucose).

Inorganic Molecule

Molecule lacking C–H bonds; often small and simple (e.g., H2O, CO2).

Hydrophilic

Polar or charged substance that dissolves readily in water.

Hydrophobic

Non-polar substance that repels water and does not dissolve (e.g., lipids).

Amphipathic

Molecule possessing both hydrophilic and hydrophobic regions (e.g., phospholipids).

Hydrogen Bond

Weak attraction between a hydrogen in one polar molecule and an electronegative atom in another.

Dehydration Synthesis

Chemical reaction that joins monomers into polymers by removing water; requires energy.

Hydrolysis

Reaction that breaks polymers into monomers by adding water; releases energy.

Macromolecule

Large organic molecule (carbohydrate, lipid, protein, nucleic acid).

Monomer

Small building block that joins to form polymers (e.g., glucose, amino acid).

Polymer

Long chain of monomers linked by covalent bonds (e.g., starch, DNA).

Carbohydrate

Organic molecule of C, H, O; includes sugars, starches, glycogen, cellulose.

Monosaccharide

Single sugar unit (e.g., glucose, fructose); carbohydrate monomer.

Disaccharide

Sugar formed by two monosaccharides joined by glycosidic linkage (e.g., sucrose).

Polysaccharide

Polymer of many monosaccharides; storage or structural (e.g., starch, glycogen, cellulose).

Glycosidic Linkage

Covalent bond connecting two monosaccharides in carbohydrates.

Lipid

Hydrophobic organic molecule largely of hydrocarbons; includes fats, phospholipids, steroids.

Saturated Fatty Acid

Fatty acid with no C=C double bonds; straight chains; solid at room temperature.

Unsaturated Fatty Acid

Fatty acid with one or more C=C double bonds; bent chains; liquid at room temperature.

Triglyceride

Lipid of glycerol bonded to three fatty acids; major energy storage form.

Phospholipid

Amphipathic lipid with glycerol, two fatty acids, and phosphate-containing head; forms cell membranes.

Steroid

Lipid with four fused hydrocarbon rings; includes cholesterol, hormones, vitamin D.

Protein

Polymer of amino acids folded into a specific 3-D shape that determines function.

Amino Acid

Protein monomer containing amino group, carboxyl group, hydrogen, and variable R group.

Peptide Bond

Covalent bond linking amino acids in a protein via dehydration synthesis.

Polypeptide

Linear chain of amino acids; folds to become a functional protein.

Primary Structure

Linear sequence of amino acids in a polypeptide.

Secondary Structure

Regular coils or folds (α-helix, β-sheet) formed by hydrogen bonding in backbone.

Tertiary Structure

Overall 3-D folding of a polypeptide driven by R-group interactions.

Quaternary Structure

Protein structure formed by association of two or more polypeptide chains.

Enzyme

Catalytic protein that accelerates biochemical reactions.

Nucleic Acid

Polymer of nucleotides; stores (DNA) or transmits (RNA) genetic information.

Nucleotide

Monomer of nucleic acids composed of a sugar, phosphate, and nitrogenous base.

Phosphodiester Bond

Covalent linkage between nucleotides’ sugar and phosphate groups in nucleic acids.

DNA (Deoxyribonucleic Acid)

Double-stranded nucleic acid with deoxyribose sugar; stores hereditary information.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid with ribose; carries genetic information for protein synthesis.

ATP (Adenosine Triphosphate)

Energy currency of cells; three phosphate bonds store potential energy for cellular work.

Catabolic Reaction

Metabolic pathway that breaks complex molecules into simpler ones, releasing energy to ATP.

Anabolic Reaction

Metabolic pathway that builds complex molecules using energy from ATP.