AP Biology - Enzymes

the laws of the thermodynamics tell us if a reaction is spontaneous, but it does not describe the ___ of the reaction

rate

protein macromolecules that catalyze reactions by lowering the Ea
not consumed by the reaction
typically only catalyze one substrate

enzymes

typically a pocket or groove on the enzyme where the side chains or R groups of the protein are exposed

active site

enzymes will change the shape of their active site to allow the substrate to bind better
brings chemical groups of the active sites into positions that enhance the ability to catalyze the chemical reaction

induced fit

efficiency of enzymes can be affected by

pH
temperature
chemicals

rate of enzyme activity ____ with temperature up to a certain point

increases

being outside the normal pH range can cause _____ in the enzyme to break due to the H+ or -OH ions, thus changing the shape of the enzyme

hydrogen bonds

non protein molecules that assist enzyme function
can be bound loosely or tightly

cofactors

consist of metals (zinc, iron, copper)

inorganic cofactors

an enzyme with the cofactor attached

holoenzyme

organic cofactors

coenzymes

example of an enzyme cofactor

vitamins

reduce the activity of specific enzymes
can be permanent or reversible

enzyme inhibitors

inhibitor binds with covalent bonds
toxins, poisons

permanent

inhibitor binds with weak interactions

reversible

reduce enzyme activity by blocking substrates from binding to the active site

competitive inhibitors

bind to an area other than the active site, which changes the shape of the active site, preventing substrates from binding

noncompetitive inhibitors

another term for the active site

allosteric site

a cell can regulate its metabolic pathways by

controlling when/where enzymes are active
switch genes that code for enzymes on/off

molecules bind to an allosteric site which changes the shape and function of the active site
may result in inhibition or stimulation

allosteric regulation

type of interaction between molecules binding to an allosteric site

noncovalent

two binding sites in allosteric enzymes

active and allosteric

substrate binds to allosteric site and stabilizes the shape of the enzyme so that the active sites remain open

allosteric activator

substrate binds to an allosteric site and stabilizes the enzyme shape so that the active sites are closed (inactive form)

allosteric inhibitor

substrate binds to one active site (on an enzyme with more than one active site) which stabilizes the active form

cooperativity

cooperativity is considered allosteric regulation since

its binding at one site

sometimes, the end product of a metabolic pathway can act as an inhibitor to an __ enzyme in the same pathway

early