[Gk. poly: many + meros: unit] A large molecule made up of similar or identical subunits called monomers. (Contrast with monomer, oligomer.)
[Gk. mono: one + meros: unit] A small molecule, two or more of which can be combined to form oligomers (consisting of a few monomers) or polymers (consisting of many monomers).
A giant (molecular weight>1,000) polymeric molecule. The macromolecules are the proteins, polysaccharides, and nucleic acids.
A characteristic combination of atoms that contribute specific properties when attached to larger molecules.
Molecules consisting of the same numbers and kinds of atoms, but differing in the bonding patterns by which the atoms are held together.
Molecules made up of the same kinds and numbers of atoms, in which the atoms are bonded differently.
A chemical reaction in which two molecules become connected by a covalent bond and a molecule of water is released (AH + BOH 〉 AB + H₂O.) (Contrast with hydrolysis reaction.)
[Gk. hydro: water + lysis: break apart] A chemical reaction that breaks a bond by inserting the components of water (AB + H₂O 〉 AH + BOH). (Contrast with condensation reaction.)
[Gk. protos: first] Long-chain polymer of amino acids with twenty different common side chains. Occurs with its polymer chain extended in fibrous proteins, or coiled into a compact macromolecule in enzymes and other globular proteins.
R group (side chain)
The distinguishing group of atoms of a particular amino acid; also known as a side chain.
The covalent bond between two sulfur atoms (-S-S-) linking two molecules or remote parts of the same molecule.
The bond between amino acids in a protein; formed between a carboxyl group and amino group (CO-NH⁻) with the loss of water molecules.
Of a protein, localized regularities of structure, such as the α helix and the β pleated sheet.
β(beta) pleated sheet
A type of protein secondary structure; results from hydrogen bonding between polypeptide regions running antiparallel to each other.
In reference to a protein, the relative locations in three-dimensional space of all atoms in the molecule. The overall shape of a protein. (Contrast with primary, secondary, and quaternary structures.)
Loss of activity of an enzyme or nucleic acid molecule as a result of structural changes induced by heat or other means.
A protein that guards other proteins by counteracting molecular interactions that threaten their three-dimensional structure.
heat shock proteins (HSPs)
Chaperone proteins expressed in cells exposed to high or low temperatures or other forms of environmental stress.
Organic compounds containign carbon, hydrogen, and oxygen in the ratio 1:2:1 (i.e., with the general formula CⁿH₂ⁿOⁿ). Common examples are sugars, starch, and cellulose.
A simple sugar. Oligosaccharides and polysaccharides are made up of monosaccharides.
A macromolecule composed of many monosaccharides (simple sugars). Common examples are cellulose and starch.
[Gk. gleukos: sugar, sweet] The most common monosaccharide; the monomer of the polysaccharides starch, glycogen and cellulose.
Bond between carbohydrate (sugar) molecules through an intervening oxygen atom (-O-).
[Gk. lipis: fat] Nonpolar, hydrophobic molecules that include fats, oils, waxes, steroids, and the phospholipids that make up biological membranes.
A three-carbon alcohol with three hydroxyl groups; a component of phospholipids and triglycerides.
A molecule made up of a long nonpolar hydrocarbon chain and a polar carboxyl group. Found in many lipids.
A condensation (water-releasing) reaction in which the carboxyl group of a fatty acid reacts with the hydroxyl group of an alcohol. Lipids are formed this way
saturated fatty acids
A fatty acid in which all the bonds between carbon atoms in the hydrocarbon chain are single bonds-that is, all the bonds are saturated with hydrogen atoms. (Contrast with unsaturated fatty acid.)
unsaturated fatty acids
A fatty acid whose hydrocarbon chain contains one or more double bonds. (Contrast with saturated fatty acid.)
[Gk. amphi: both + pathos: emotion] Of a molecule, having both hydrophilic and hydrophobic regions.
A structure that is two layers in thickness. In biology, most often refers to the phospholipid bilayer of membranes.
The basic structural unit of biological membranes; a sheet of phospholipids two molecules thick in which the phospholipids are lined up with their hydrophobic "tails" packed tightly together and hydrophilic, phosphate-containing "heads" facing outward. Also called lipid bilayer.