AP Biology Unit 1 Vocabulary: Chemistry of Life

Polar molecule

A molecule with uneven distribution of charges (like water) due to unequal sharing of electrons.

Hydrogen bond

Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen in water).

Cohesion

Water molecules sticking to each other through hydrogen bonds.

Adhesion

Water molecules sticking to other substances (e.g., plant cell walls).

Surface tension

A result of cohesion; water molecules form a 'skin' at the surface.

Capillary action

Movement of water through narrow spaces due to cohesion + adhesion.

High specific heat

Water can absorb lots of heat before its temperature rises.

Heat of vaporization

Amount of heat needed to convert liquid water into gas.

Universal solvent

Water's ability to dissolve many substances due to its polarity.

Hydrophilic

'Water-loving' — substances that dissolve easily in water.

Hydrophobic

'Water-fearing' — substances that do not dissolve in water (nonpolar).

Carbon

A key element in all organic molecules; forms 4 stable covalent bonds.

Hydrogen

Found in all organic molecules; part of water and hydrocarbons.

Oxygen

Electronegative atom in water and organic molecules; used in cellular respiration.

Nitrogen

Found in amino acids and nucleotides.

Phosphorus

Found in phospholipids and nucleic acids (e.g., DNA backbone).

Sulfur

Found in some amino acids; forms disulfide bonds in proteins.

Organic molecule

Molecule that contains carbon and is found in living things.

Covalent bond

Strong bond formed by sharing electrons between atoms.

Nonpolar covalent bond

Electrons shared equally (no charge difference).

Polar covalent bond

Electrons shared unequally, leading to partial charges.

Molecular structure

The shape/arrangement of atoms in a molecule.

Isomer

Molecules with the same formula but different structures (e.g., glucose & fructose).

Macromolecule

A large molecule made of smaller subunits (e.g., proteins, carbs).

Monomer

A single building block of a macromolecule (e.g., glucose).

Polymer

A chain of monomers linked together.

Dehydration synthesis

Chemical reaction where two monomers join and release a water molecule.

Hydrolysis

Reaction where a polymer is broken apart by adding water.

Monosaccharide

Simple sugar (e.g., glucose, fructose).

Disaccharide

Two sugars joined together (e.g., sucrose = glucose + fructose).

Polysaccharide

Long chain of sugars (e.g., starch, glycogen, cellulose).

Glycosidic linkage

Covalent bond joining two monosaccharides.

Fatty acid

Long hydrocarbon chain with a carboxyl group; part of fats.

Glycerol

A 3-carbon molecule that joins with fatty acids to form triglycerides.

Triglyceride

Lipid made of 3 fatty acids + 1 glycerol; stores energy.

Phospholipid

Lipid with 2 fatty acids, 1 glycerol, and a phosphate group; makes up cell membranes.

Steroid

Lipid with 4 fused carbon rings (e.g., cholesterol, hormones).

Saturated fat

Fat with no double bonds; solid at room temp (e.g., butter).

Unsaturated fat

Fat with one or more double bonds; liquid at room temp (e.g., olive oil).

Amphipathic

Molecule with both hydrophilic and hydrophobic parts (e.g., phospholipids).

Amino acid

Monomer of protein; contains amino, carboxyl, and R-group.

Peptide bond

Covalent bond between amino acids.

Polypeptide

Long chain of amino acids.

R-group

Variable group in amino acids; determines properties.

Enzyme

Protein that speeds up chemical reactions.

Catalyst

Substance that increases reaction rate without being used up.

Nucleotide

Monomer of DNA/RNA; contains sugar, phosphate, nitrogen base.

Nitrogenous base

A, T, G, C in DNA; A, U, G, C in RNA.

Phosphodiester bond

Bond between phosphate and sugar in nucleic acids.

DNA

Double-stranded nucleic acid with deoxyribose sugar; stores genetic info.

RNA

Single-stranded nucleic acid with ribose sugar; helps make proteins.

Double helix

Shape of DNA formed by base pairing and twisting.

Antiparallel

DNA strands run in opposite directions (5'→3' and 3'→5').

5' to 3' direction

Direction in which nucleotides are added to DNA/RNA.

Base pairing

A-T and G-C in DNA; A-U and G-C in RNA.

Primary structure

Sequence of amino acids.

Secondary structure

Local folding into alpha helices or beta sheets.

Tertiary structure

3D shape of a single polypeptide.

Quaternary structure

Combination of multiple polypeptides.

Denaturation

Loss of protein shape and function due to pH, temperature, etc.

Disulfide bridges

Strong covalent bonds that help stabilize tertiary structure.

Hydrogen bonding

Helps maintain secondary and tertiary protein structure.

Deoxyribose

5-carbon sugar in DNA.

Ribose

5-carbon sugar in RNA.

Purine

Double-ring nitrogen bases (Adenine and Guanine).

Pyrimidine

Single-ring nitrogen bases (Cytosine, Thymine, Uracil).

Complementary base pairing

A pairs with T (or U), G pairs with C.

Hydrogen bonds (in DNA)

Hold base pairs together.

Sugar-phosphate backbone

Repeating pattern of sugar and phosphate in DNA/RNA.

Abiogenesis

Life originated from non-living chemical systems.

Miller-Urey experiment

Showed that simple organic molecules could form under early Earth conditions.

Protocell

Simple vesicle-like structure that may have led to the first cells.

RNA World Hypothesis

Theory that RNA was the first genetic material capable of self-replication.

Ribozyme

RNA molecule that acts like an enzyme.