enzymes

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^______