Bio Ch.3
peptide bond
A distinctive covalent carbon-to-nitrogen bond that links amino acids in peptides and proteins.
ribonucleic acid (RNA)
A family of single-stranded nucleic acids that function mainly in protein synthesis
protein
A large, complex organic compound composed of covalently linked amino acid subunits; contains carbon, hydrogen, oxygen, nitrogen, and sulfur.
fatty acid
A lipid that is an organic acid containing a long hydrocarbon chain, with no double bonds (saturated fatty acid), one double bond (monounsaturated fatty acid), or two or more double bonds (polyunsaturated fatty acid); components of triacylglycerols and phospholipids, as well as monoacylglycerols and diacylglycerols.
polymer
A molecule built up from repeating subunits of the same general type (monomers); examples include proteins, nucleic acids, or polysaccharides.
nucleotide
A molecule consisting of one or more phosphate groups, a five-carbon sugar (ribose or deoxyribose), and a nitrogenous base (purine or pyrimidine).
monomer
A molecule that can link with other similar molecules; two monomers join to form a dimer, whereas many form a polymer. Monomers are small (e.g., sugars or amino acids) or large (e.g., tubulin or actin proteins).
methyl group
A nonpolar functional group; abbreviated ---CH3.
carbonyl group
A polar functional group consisting of a carbon attached to an oxygen by a double bond; found in aldehydes and ketones.
condensation synthesis
A reaction in which two monomers are combined covalently through the removal of the equivalent of a water molecule. Compare with hydrolysis.
secondary structure (of a protein)
A regular geometric shape produced by hydrogen bonding between the atoms of the uniform polypeptide backbone; includes the alpha helix and the betapleated sheet. Compare with primary, tertiary, and quaternary protein structure.
cellulose
A structural polysaccharide consisting of beta glucose subunits; the main constituent of plant primary cell walls.
monosaccharide
A sugar that cannot be degraded by hydrolysis to a simpler sugar (e.g., glucose or fructose).
glycerol
A three-carbon alcohol with a hydroxyl group on each carbon; a component of triacylglycerols and phospholipids, as well as monoacylglycerols and diacylglycerols.
macromolecule
A very large organic molecule, such as a protein or nucleic acid.
phosphate group
A weakly acidic functional group that can release one or two hydrogen ions.
carboxyl group
A weakly acidic functional group; abbreviated ---COOH.
amino group
A weakly basic functional group; abbreviated ---NH2.
enzyme
An organic catalyst (usually a protein) that accelerates a specific chemical reaction by lowering the activation energy required for that reaction.
amino acid
An organic compound containing an amino group (---NH2) and a carboxyl group (---COOH); may be joined by peptide bonds to form a polypeptide chain.
lipid
Any of a group of organic compounds that are insoluble in water but soluble in nonpolar solvents; lipids serve as energy storage and are important components of cell membranes.
steroids
Complex molecules containing carbon atoms arranged in four attached rings, three of which contain six carbon atoms each and the fourth of which contains five, e.g., cholesterol and certain hormones, including the male and female sex hormones of vertebrates.
carbohydrate
Compound containing carbon, hydrogen, and oxygen, in the approximate ratio of C:2H:O, e.g., sugars, starch, and cellulose.
phospholipids
Lipids in which two fatty acids and a phosphorus-containing group are attached to glycerol; major components of cell membranes.
pyrimidines
Nitrogenous bases, each composed of a single ring of carbon and nitrogen atoms, e.g., thymine, cytosine, and uracil; components of nucleic acids. Compare with purines.
geometric isomer
One of two or more chemical compounds having the same arrangement of covalent bonds but differing in the spatial arrangement of their atoms or groups of atoms.
structural isomer
One of two or more chemical compounds having the same chemical formula but differing in the covalent arrangement of their atoms, e.g., glucose and fructose.
NAD+/NADH
Oxidized and reduced forms, respectively, of nicotinamide adenine dinucleotide, a coenzyme that transfers electrons (as hydrogen), particularly in catabolic pathways, including cellular respiration.
deoxyribose
Pentose sugar lacking a hydroxyl (---OH) group on carbon-2 ; a constituent of DNA.
hydroxyl group
Polar functional group; abbreviated ---OH.
hydrolysis
Reaction in which a covalent bond between two subunits is broken through the addition of the equivalent of a water molecule; a hydrogen atom is added to one subunit and a hydroxyl group to the other. Compare with condensation synthesis.
ATP
See adenosine triphosphate.
saturated fatty acid
See fatty acid.
unsaturated fatty acid
See fatty acid.
dipeptide
See peptide.
polypeptide
See peptide.
primary structure (of a protein)
The complete sequence of amino acids in a polypeptide chain, beginning at the amino end and ending at the carboxyl end. Compare with secondary, tertiary, and quaternary protein structure.
ribose
The five-carbon sugar present in RNA and in important nucleoside triphosphates such as ATP.
triacylglycerol
The main storage lipid of organisms, consisting of a glycerol combined chemically with three fatty acids; also called triglyceride. Compare with monoacylglycerol and diacylglycerol.
quaternary structure (of a protein)
The overall conformation of a protein produced by the interaction of two or more polypeptide chains. Compare with primary, secondary, and tertiary protein structure.
tertiary structure (of a protein)
The overall three-dimensional shape of a polypeptide that is determined by interactions involving the amino acid side chains. Compare with primary, secondary, and quaternary protein structure.
glycogen
The principal storage polysaccharide in animal cells; formed from glucose and stored primarily in the liver and, to a lesser extent, in muscle cells.
enantiomers
Two isomeric chemical compounds that are mirror images.