alpha (α) helix
A spiral shape constituting one form of the secondary structure of proteins, arising from a specific hydrogen-bonding structure.
The opposite arrangement of the sugar-phosphate backbones in a DNA double helix.
beta (β) pleated sheet
One form of the secondary structure of proteins in which the polypeptide chain folds back and forth. Two regions of the chain lie parallel to each other and are held together by hydrogen bonds.
A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).
A protein molecule that assists the proper folding of other proteins.
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.
A biological compound consisting of three fatty acids linked to one glycerol molecule.
A long carbon chain carboxylic acid. Varies in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form fat.
An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.
A covalent bond formed between two monosaccharides by a dehydration reaction.
One of a family of compounds, including fats, phospholipids, and steroids, that are insoluble in water.
A giant molecule formed by the joining of smaller molecules, usually by a condensation reaction. Polysaccharides, proteins, and nucleic acids are _________.
The simplest carbohydrate, active alone or serving as a monomer for disaccharides and polysaccharides. Also known as simple sugars, the molecular formulas of _________ are generally some multiple of CH2O.
A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.
The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group.
The covalent bond between two amino acid units, formed by a dehydration reaction.
The level of protein structure referring to the specific sequence of amino acids.
A three-dimensional biological polymer constructed from a set of 20 different monomers called amino acids.
A molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail.
A polymer consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.
A polymer (chain) of many amino acids linked together by peptide bonds.
The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.
ribonucleic acid (RNA)
A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in protein synthesis and as the genome of some viruses.
saturated fatty acid
A fatty acid in which all carbons in the hydrocarbon tail are connected by single bonds, thus maximizing the number of hydrogen atoms that can attach to the carbon skeleton.
The localized, repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bond formation between peptide linkages.
A storage polysaccharide in plants consisting entirely of glucose.
A type of lipid characterized by a carbon skeleton consisting of four rings with various functional groups attached.
Irregular contortions of a protein molecule due to interactions of side chains involved in hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
Three fatty acids linked to one glycerol molecule.
unsaturated fatty acid
A fatty acid possessing one or more double bonds between the carbons in the hydrocarbon tail. Such bonding reduces the number of hydrogen atoms attached to the carbon skeleton.
A technique that depends on the diffraction of an X-ray beam by the individual atoms of a molecule to study the three-dimensional structure of the molecule.