ENZYMES 2-4 http://www.biologie.uni-hamburg.de/b-online/library/cat-removed/enzyme_.gif

Chemical reactions need help to get started. Ex: A fire needs a match to get it started. http://www.chuckwagondiner.com/art/matches.jpg http://plato.acadiau.ca/COURSES/comm/g5/Fire_Animation.gif

______________ to get a chemical reaction _______________ = ________________________ Energy required STARTED ACTIVATION ENERGY ACTIVATION ENERGY REACTANTS PRODUCTS Image from: Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved

___________ HELP CHEMICAL REACTIONS _______________ HAPPEN FASTER Image from: Pearson Education Inc, publishing as Pearson Prentice Hall. All rights reserved CATALYSTS ___________ HELP CHEMICAL REACTIONS _______________ HAPPEN FASTER Catalysts work by ____________ the ___________________________to get a chemical reaction started. DECREASING ACTIVATION ENERGY required

IT’S LIKE PUSHING A SNOWBALL UP A HILL Once it gets to top . . . it can roll back all by itself http://www.gifs.net

CATALYSTS in Living Things Image from: http://www.hillstrath.on.ca/moffatt/bio3a/digestive/enzanim.htm CATALYSTS in Living Things In living systems __________ that ________________to control chemical reactions are called = _________ PROTEINS act as catalysts ENZYMES SEE ANIMATION of AMYLASE More about this in Chapters 7,8,9 and 12

Click the image to play the video segment. Enzymatic Reactions 2D Click the image to play the video segment. Video 4

PROTEINS CAN BE ENZYMES ACTIVE SITE ENZYME SUBSTRATE ENZYME-SUBSTRATE COMPLEX ENZYME Unchanged & Reusable PRODUCTS Image modified from: http://www.biologie.uni-hamburg.de/b-online/library/cat-removed/enzyme_.gif Arrow: http://www.gifanimations.com/action/ImageDisplay/1/2/11/next

Click HERE to learn more about enzymes ENZYMES _____ like a _______________ to only _________of _________. Enzymes are ___________ by the reaction and ___________ FIT LOCK AND KEY SUBSTRATE ONE KIND UNCHANGED REUSABLE http://www.grand-illusions.com/images/articles/toyshop/trick_lock/mainimage.jpg

FACTORS THAT AFFECT ENZYME ACTIVITY __________ & ______________ Conditions that are TOO ACIDIC or TOO HOT cause proteins to ________ or _________ pH temperature UNWIND DENATURE See a movie Choose narrated http://www.desktopfotos.de/Downloads/melt_cd.jpg http://www.nealbrownstudio.com/adm/photo/163_nb_fried_egg.jpg

changes shape ACTIVE SITE CAN’T BIND Denaturing _______ the _______ of the ______________ so enzyme ______________ to ____________ changes shape ACTIVE SITE CAN’T BIND SUBSTRATE _______________ (keeping pH and temperature constant) is ______________ for maintaining ____________________ HOMEOSTASIS IMPORTANT ENZYME FUNCTION Image modified from: http://www.lewport.wnyric.org/jwanamaker/animations/Enzyme%20activity.html

-ASE Many enzyme NAMES end in _____ and the beginning of the name tells what it does DNA Polymerase= “polymerizes” joins monomers to make DNA Protease= breaks down proteins ATP synthase= synthesizes ATP

Other Factors That Influence Enzyme Activity Cofactors & Coenzymes Inhibitors From the Virtual Cell Biology Classroom on ScienceProfOnline.com Image: Animation of Enzyme, Wiki

More about Enzymes I. Sometimes an enzyme needs help Helper molecules are called cofactors (or coenzymes) Could be inorganic like a metal ion (zinc) or vitamins (like vitamin B) Could be organic coenzyme (like CoA, NAD)

Co-Factors

II. Inhibitory Molecules A. Competitive inhibitors Fit in active site but are not changed; prevent normal substrate from binding, prevent reaction. B. Non-competitive inhibitors Bind permanently to other site which changes molecular shape; prevents reaction. Allosteric inhibitor

Competitive Inhibition The inhibitor is able to fit into the active site. The inhibitor isn’t altered by the enzyme. As long as the inhibitor is in the active site, the substrate cannot enter the active site and react. .

Competitive Inhibition The more inhibitor molecules that are present, the more often one of them occupies the active site Some competitive inhibitors bind irreversibly to the active site. Others bind to the site for some time and slow down the activity of the enzyme

Competitive Inhibitors -compete for the active site 1. Penicillin competes for the active site of an enzyme used by certain bacteria

Noncompetitive Inhibitors: Allosteric sites Do not compete for the enzyme’s active site. Interact with another part of the enzyme called the allosteric site. Inhibitor is not reacted, but causes a shape change in the protein. The substrate no longer fits in the active site, so it is not chemically changed either.

Non-competitive Inhibitors - attach to an allosteric site