The Chemical Basis of Life - Organic Molecules (Video)

Vocabulary flashcards covering key concepts and terms from the notes on organic molecules and the four major biomolecule classes.

Organic molecule

Molecule containing carbon (often with hydrogen); abundant in living organisms and capable of forming macromolecules.

Inorganic molecule

Molecule that does not contain carbon-hydrogen bonds; examples include water and many salts.

Macromolecule

A large, complex organic molecule such as a protein, nucleic acid, polysaccharide, or lipid.

Monomer

A small building-block molecule that links to form polymers; some monomers have additional functions.

Polymer

A long molecule made up of many repeating monomer units.

Condensation (dehydration) reaction

Links monomers to form polymers by removing a molecule of water; catalyzed by enzymes.

Hydrolysis

Breaks polymers into monomers by adding water; catalyzed by enzymes.

Functional group

A group of atoms with characteristic chemical features that impart reactivity and properties to molecules.

Nonpolar bond

Covalent bond with even sharing of electrons; typically results in hydrophobic behavior.

Polar bond

Covalent bond with unequal sharing of electrons; creates partial charges and often increases solubility in water.

Carbon skeleton

The chain or ring of carbon atoms that forms the backbone of organic molecules.

Hydrophobic

Water-fearing; nonpolar; tends to avoid water.

Hydrophilic

Water-loving; polar or charged; tends to dissolve in water.

Hydrocarbon

Organic molecule composed mainly of carbon and hydrogen; often nonpolar and water-insoluble.

Valence (carbon)

Carbon can form up to four covalent bonds to complete its outer shell.

Covalent bond

Bond formed by sharing electrons between two atoms.

Isomer

Two molecules with the same molecular formula but different structures or properties.

Structural isomer

Isomers with the same atoms arranged differently, yielding different bonding relationships.

Stereoisomer

Isomers with the same bonding pattern but different spatial arrangement.

Cis-trans isomer

A type of stereoisomer around a double bond; cis = same side, trans = opposite sides.

Enantiomer

A pair of mirror-image isomers that are not superimposable.

D-glucose / L-glucose

Enantiomeric forms of glucose; mirror images with different biological activity.

Monosaccharide

The simplest sugar; includes pentoses (five carbons) and hexoses (six carbons; e.g., glucose).

Pentose

Five-carbon sugar.

Hexose

Six-carbon sugar (e.g., glucose).

Glucose

A common hexose sugar; C6H12O6; major nutrient for cells.

Disaccharide

Carbohydrate formed by two monosaccharides linked by a glycosidic bond; broken by hydrolysis.

Sucrose

Disaccharide composed of glucose and fructose.

Lactose

Disaccharide composed of galactose and glucose.

Maltose

Disaccharide composed of two glucose units.

Polysaccharide

Polymers formed from many monosaccharides; energy storage or structural roles.

Starch

Plant storage polysaccharide with primarily a-1,4 linkages; energy reserve.

Glycogen

Animal storage polysaccharide; highly branched with a-1,4 and a-1,6 linkages.

Cellulose

Structural polysaccharide in plants; β-1,4-glycosidic linkages; forms straight, rigid fibers.

Chitin

Structural polysaccharide in arthropod exoskeletons and fungi; similar to cellulose with N-acetylglucosamine.

Glycosaminoglycans

Structural polysaccharides in cartilage and extracellular matrix.

Peptidoglycan

Structural component of bacterial cell walls.

Lipid

Diverse group of hydrophobic molecules; nonpolar; includes fats, phospholipids, steroids, waxes.

Fat (triacylglycerol)

Glycerol molecule with three fatty acids; energy storage and insulation; formed by dehydration.

Fatty acid

Carboxyl group attached to a long hydrocarbon chain; varies in length and degree of unsaturation.

Saturated fatty acid

Fatty acid with only single C–C bonds; typically solid at room temperature.

Unsaturated fatty acid

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

Cis forms

Naturally occurring arrangement of double-bonded fatty acids with hydrogens on the same side; usually liquid.

Trans fats

Hydrogenated fatty acids with double bonds in the trans configuration; associated with health risks.

Phospholipid

Lipid with two fatty acids and a phosphate group attached to glycerol; amphipathic; major membrane component.

Amphipathic

Molecule having both hydrophobic and hydrophilic regions.

Steroid

Lipid with four fused hydrocarbon rings; nonpolar; examples include cholesterol, hormones.

Cholesterol

Steroid lipid; important membrane component and hormone precursor.

Protein

Macromolecule with diverse functions; built from amino acids; 20 standard amino acids; R-group determines properties.

Amino acid

Organic molecule with amino and carboxyl groups; central α-carbon; side chain (R group) determines identity.

R group (side chain)

Variable side chain of an amino acid that determines its properties.

Peptide bond

Covalent bond formed by a dehydration reaction between the carboxyl group of one amino acid and the amino group of the next.

Polypeptide

Polymer of amino acids; may consist of one or several polypeptide chains; length ranges from a few to thousands.

N-terminus

Amino terminus of a polypeptide; the free end with an amino group.

C-terminus

Carboxyl terminus of a polypeptide; the free end with a carboxyl group.

Primary structure

Linear sequence of amino acids in a polypeptide; encoded by genes; held by peptide bonds.

Secondary structure

Local folding stabilized by hydrogen bonds between CO and NH groups; includes alpha helices and beta sheets.

Tertiary structure

Three-dimensional folding of a single polypeptide driven by side-chain interactions (electrostatic, hydrogen, Van der Waals) and disulfide bridges.

Quaternary structure

Complex formed by two or more polypeptide chains (subunits); may be identical or different.

Hydrogen bond (proteins)

Noncovalent attraction between a partial positive H and a electronegative atom (O or N) that helps stabilize structures.

Disulfide bridge

Covalent bond between sulfur atoms (often in cysteine) that helps stabilize protein structure.

Hydrophobic effect

Tendency of nonpolar amino acid side chains to cluster away from water, driving protein folding.

Van der Waals forces

Weak noncovalent interactions between closely spaced atoms that contribute to protein folding and stability.

Protein-protein interactions

Specific binding between proteins essential for cellular processes; rely on complementary surfaces and noncovalent bonds.

Nucleic acid

Biological macromolecule that stores and transmits hereditary information; includes DNA and RNA.

DNA (deoxyribonucleic acid)

Stores genetic information; double-stranded, helical; sugar is deoxyribose; bases A, T, G, C with A–T and G–C pairing.

RNA (ribonucleic acid)

Decodes DNA to synthesize proteins; usually single-stranded; sugar is ribose; bases A, U, G, C with A–U and G–C pairing.

Nucleotide

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

Phosphodiester bond

Bond linking nucleotides via dehydration to form the sugar-phosphate backbone.

Sugar-phosphate backbone

The repeating pattern of sugar and phosphate groups that forms the backbone of nucleic acids.

Double helix

Structure of DNA where two polynucleotide strands coil around a common axis.

Base pairing

Adenine pairs with thymine (DNA) or uracil (RNA); cytosine pairs with guanine.

Complementary base pairing

Specific pairing rule (A-T/U, C-G) that enables accurate replication and transcription.

Single strand

A nucleic acid molecule lacking a second complementary strand; typical of RNA.

tRNA (transfer RNA)

RNA molecule that helps translate mRNA codons into amino acids during protein synthesis.