activation energy
minimum energy needed for a chemical reaction to initiate
active site
place on an enzyme where the substrate binds and the reaction occurs
allosteric regulation
type of enzyme regulation in which the location at which the regulatory molecule binds is not the same as the active site
alpha helix
helical structure of proteins that adopts a right-handed-spiral conformation where chain backbone groups form hydrogen bonds with groups of nearby amino acids along the protein chain
amino acid
organic molecule that contains a carboxyl group (), an amino group (), and a functional side chain, which is a group of atoms unique in its structure and function
amino group
portion of an amino acid made up of a nitrogen atom bonded to two hydrogen atoms ()
beta sheet
structure of amino acids that takes the shape of a pleated sheet folded at regular intervals
carboxyl group
portion of a molecule made of a carbon atom bonded to one oxygen atom and one hydroxyl group ()
catalyst
substance that causes the rate of a chemical reaction to increase
competitive inhibitor
enzyme inhibitor in which the inhibitor binds to the active site
conformation
shape and configuration of a protein backbone and side chains
enzyme
substance, usually a protein, that speeds up a biological reaction without being consumed in the reaction
feedback inhibition
type of enzyme inhibition in which an increasing concentration of product inhibits the enzyme activity, stopping the reaction
inhibitor
molecule (other than the products of the reaction) that decreases the rate of reaction
metabolic pathway
series of chemical reactions that occur in a living organism and may be facilitated by enzymes. The products of one set of enzymatic reactions serve as the reactants for a different enzymatic reaction.
noncompetitive inhibition
type of enzyme inhibition in which the inhibitor does not bind to the active site and may bind to either the enzyme or the enzyme-substrate complex
peptide bond
covalent bond formed between an amino group and a carboxyl group on neighboring amino acids
polypeptide chain
linear molecule consisting of amino acids connected by peptide bonds
primary structure
sequence of amino acids linked by peptide (amide) bonds to form a polypeptide chain
quaternary structure
two or more polypeptide chains that interact with one another
R group
one of the 20 possible groups that give amino acids their distinct chemical identities
secondary structure
structure of a protein that is the initial folding of the amino acid polymer that arises from hydrogen bonding between the amine and carboxyl groups of amino acids in neighboring parts of the chain
substrate
molecule that is acted upon by an enzyme by binding to the enzyme's active site
subunit
single polypeptide chain that is part of a larger, multi-subunit protein
tertiary structure
structure of a protein produced by interactions between the R groups of the amino acids in the chain and with the environment around them