catalyst
substance that increases the rate of a chemical reaction without itself being changed in the process
enzyme
a biological catalyst, usually a protein
enzymology
the study of enzymes
substrate
substance acted upon by the enzyme
active site
region on the enzyme where the substrate binds and the chemical reaction occurs
allosteric site
site where a substance binds that alters the behavior of the enzyme
coenzyme
molecule that is independently synthesized and incorporated into the protein structure of the enzyme; provides opportunity for chemical reaction that may not be possible with the protein structure alone; commonly referred to as a cofactor when it contains a metal
inhibitor
substance that blocks activity of the enzyme
activator
a substance that enhances activity of the enzyme
higher
enzymes provide _______ reaction rates
conditions
enzymes cause milder reaction ___________
specificity
enzymes provide greater ___________
regulation
enzymes create a greater capacity for ________
transferases
catalyze transfer of a functional group from one molecule to another
hydrolases
catalyze bond cleavage by the introduction of water
isomerases
catalyze reactions involving intramolecular rearrangements
different path
the first law of thermodynamics states that energy cannot be created or destroyed; enzymes allow a reaction to take a _________
favorably
the second law of thermodynamics states that reactions trend toward greater entropy; enzyme structure orients reactants __________ using one or more active sites
transition state theory
A+B 🡪 Xǂ 🡪 P + Q
transition state
short-lived, high-energy state which represents both the reactants and the products; Exists at the top of the curve representing the free energy barrier or activation energy.
barrier of activation
barrier which must be overcome in order for a reaction to go to completion, also termed the energy of activation
Arrhenius equation
reaction is path independent; energy of activation involves contributions from both entropy and enthalpy
catalysts
all __________ function by decreasing the energy of activation required for the reaction
decreasing
all catalysts function by _________ the energy of activation
effective concentration
proximity and orientation effects increase the ______________, reducing the amount of entropy decrease required (lowers activation nrg)
active site specificity, substrate channels
proximity and orientation effects are accomplished by ________________ and _____________
active site specificity
enzyme selectively binds the substrate; functional groups are oriented such that only the substrate binds favorably
substrate channel
protein shape orients and directs the substrate to the active site region
acid-base catalysis
proton donors and acceptors in an active site catalyze the reaction
pH
acid-base catalysis reactions alter in activity as _______ changes
first order
reaction whose rate depends on the first power of the reactant concentration
k[A]
rate =
half life
the time required for something to fall to half its initial value
-k1 t
[A] / [A0] = e^______