1. ENZYMES 2-4

2. Chemical reactions need help to get started.
Ex: A fire needs a match to get it started.

3. ______________ to get a chemical reaction _______________
= ________________________
Energy required
STARTED
ACTIVATION ENERGY
ACTIVATION ENERGY
REACTANTS
PRODUCTS
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4. ___________ 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

5. IT’S LIKE PUSHING A SNOWBALL UP A HILL
Once it gets to top . . .
it can roll back all by itself

6. CATALYSTS in Living Things
Image from:
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

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

8. PROTEINS CAN BE ENZYMES
ACTIVE SITE
ENZYME
SUBSTRATE
ENZYME-SUBSTRATE
COMPLEX
ENZYME Unchanged
& Reusable
PRODUCTS
Image modified from:
Arrow:

9. 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

10. 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

11. 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:

12. -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

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

14. 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)

15. Co-Factors

16. 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

17. 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. .

18. 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

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

20. 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.

21. Non-competitive Inhibitors - attach to an allosteric site