ACTIVITY #13: ENZYMES
Enzyme
Catalyst
Substrate
Activation energy
Active site
Denaturation
VOCABULARY
Some chemical reactions would be too slow orhave too high of an activation energy withouta little help
Catalyst: a substance that speeds up achemical reaction
Works by lowering the activation energy
Cells make special proteins called enzymes toact as catalysts for chemical reactions
One type of enzyme for each type of chemicalreaction
Its shape makes it specific for its job
ENZYMES
ACTIVATION ENERGY
Would the hill behigher or lowerwith an enzymepresent?
Lower
1.Provide a site for the reactants to be broughttogether to react
2.Help to break the bonds of the reactants
Reduces the energy needed for the reaction
“Enzyme Catalyzed Reaction”- a reactionsped up by an enzyme
HOW DO ENZYMES WORK?
Substrates- what the reactants are calledin an enzyme catalyzed reaction
Bind to a place on the enzyme called theactive site which has a specific shape
SUBSTRATE
1."Lock and Key Model": substrates fit theactive site of an enzyme like a key fits into alock
A very specific interaction!
Provides the site for the reactants to cometogether
2 MODELS HELP EXPLAIN HOW ENZYMESWORK
Substrate Enzyme
2.“Induced-fit Model”:enzyme binds thesubstrate(s) andslightly changes itsshape to “hug” thesubstrate(s) tightly(like a handshake)
Places “strain” onexisting bonds,allowing bonds tobreak and thechemical reaction togo forward
Example of an enzyme-catalyzedreaction: ____________ is formedby combining___________________ andwater in the presence of theenzyme“_______________________”.
Carbonic Acid
Carbon dioxide
Carbonic anhydrase
After the product isreleased from theenzyme, the enzymeis recycled and usedagain
Enzymes arereusable!
WHY AREN’T ENZYMES CONSIDEREDA REACTANT OR A PRODUCT?
1.protease- any enzyme that speeds hydrolysisor breakdown of proteins
2.sucrase (a disaccharidease) - an enzymewhich speeds the breakdown of .
3.lipase - any enzyme which speeds thebreakdown of
4.nuclease - any enzyme which speeds thebreakdown of
5.amylase - an enzyme which speeds thebreakdown of amylose (=starch!)
COMMON HYDROLYTIC ENZYMES(THE SUFFIX "–ASE" COMMONLY INDICATES THAT A PROTEINIS AN ENZYME)
Sucrose
Lipids
Nucleic acids
Temperature, pH, and regulatory moleculesaffect enzyme activity
An increase in temperature will increase the rate of areaction to a certain point
After that point, the enzyme will no longer work
FACTORS AFFECTING ENZYMEACTIVITY
Denaturation - when a protein unfolds andloses its overall shape (and thus function) dueto increased temp or changes in pH
Denatured enzymes lose the shape of their active siteand will no longer function
DENATURATION
Think!
Why are temperature and pHimportant factors inmaintaining homeostasis?
If they are not maintainedthen proteins, includingenzymes, would denatureand chemical reactionscould not occur!
