Transcript Enzymes: Biological Catalysts

Enzymes: Biological Catalysts
Chapter 5.14-5.16
 Special group of
biomolecules, usually
proteins.
 Help make chemical
reactions happen … rxns
necessary for life functions!
 “Biological catalysts” speed up rates of reactions
 Function based on shape.
 Shape based on chemical
composition & environmental
conditions.
Enzyme Reactions
Metabolism: Complete set of
chemical rxns in a body.
Enzymes catalyze these
rxns.
Divided into 2 types of rxns:
a. Catabolic: Lg.
Complex molecules broken
down to simpler ones &
release energy.
b. Anabolic: Building
larger molecules fr. Smaller
ones
(energy input)
Example of Enzyme Reactions
Lactase: Breaks down lactose (milk sugars)
Pepsin: Breaks down proteins
DNA Polymerase: Adds nucleic acid bases to
growing DNA strands during DNA replication.
Kinase: attaches phosphate groups; ATP production
Enzymes speed reactions up!
 Chemical Rxns require reactants
collide/contact
Reactants ----> Products
 Enzymes make it easier for
reactions to occur by putting stress
on specific bonds or atoms w/in
molecules.
 Lower ACTIVATION ENERGY
needed for rxns. To procede
(These rxns would occur anyway,
but @ slower rate)
Enzymes lower activation energy
ACTIVATION ENERGY = Energy needed to “jump start” rxn
(energy required for rxn to proceed)
Enzyme-Substrate Complex
Substrate = Reactant
molecules; fit into
enzymes.
ACTIVE SITE: Location
where substrate binds.
Enzyme will only bind to
specific substrates based
on SHAPE!
(Lock & Key fit)
Enzymes in Action
a.
b.
Reactant
Active site
c. enzyme
d. products
Enzyme shape is important to fxn
Enzyme fxn depends on
shape of active site.
Shape of enzyme can be
affected by …
 Temperature?
 pH?
 Presence of other
binding molecules
(inhibitors or “helpers”)
Lab: Part 1
Objectives:
1. Observe reaction catalyzed by CATALASE.
H2O2 ----------------------> H2O
Hydrogen Peroxide
water
+
O2
oxygen
2. Determine if enzymes are reusable or are they changed by
the reactions they catalyze.
Lab: Part 2
Objectives:
1. Determine the optimal temperature and pH conditions of catalase.
H2O2 ----------------------> H2O
Hydrogen Peroxide
water
+
O2
oxygen
2. Identify conditions that cause denaturation and explain how
denaturation influences enzyme activity.
Enzymes & Cofactors (Coenzymes)
Cofactors = non-protein helpers; when present, they bind to
enzymes and improve “induced fit” or activate enzyme
Ex; zinc, iron, copper
Co-enzymes: organic helpers (vitamins)
Enzyme Inhibitors Stop Enzyme Action
Competitive inhibitor = molecule w/ similar shape to
substrate; competes w/ substrate for active site;
interferes w/ enzyme rxn.
Can be overcome by increasing [substrate].
Ex: Antibiotics compete w/
substrate that binds to
bacterial enzymes that make
components of cell walls.
Bacteria cannot construct
cell walls!
Enzyme Inhibitors Stop Enzyme Action
Non-competitive inhibitor = molecule binds to enzyme,
NOT IN ACTIVE SITE  causes a change in shape of
the enzyme  enzyme cannot bind to substrate
• Can be reversed when inhibitor is removed.
•
http://www.biologycorner.com/worksheets/enzyme_practice.html
•
http://www.dnatube.com/video/307/How-enzymes-work
http://www.youtube.com/watch?v=Tn7HJphCBgc
Enzymes (inhibitors, etc.)
http://www.youtube.com/watch?v=AKyyvuOmXq0&feature=related