Download Chemical Reactions and Enzymes

Chemical Reactions
and
Enzymes
Objectives
• Identify the parts of a chemical reaction.
• Relate energy changes to chemical reactions.
– interpret energy diagrams
• Summarize the importance of enzymes in
living things.
–
–
–
–
enzymes (definition)
“lock and key” model
effect of temp. and pH on enzyme activity
effect of concentration on enzyme activity
Chemical Reactions
• Definition
– process by which atoms or groups of
atoms in substances are reorganized into
different substances
• Chemical bonds are broken and/or
formed.
Chemical Equations
• Reactants
Products
“yields”
• Read the following:
C6H12O6 + 6O2 --> 6H20 + 6CO2
glucose
oxygen
water
carbon dioxide
Energy of Reactions
• Energy
– needed to start chemical reactions
• Activation Energy (Ea)
– minimum amount of energy needed for reactants
to form products
• Energy Change (
H)
– (Energy of Reactants - Energy of Products)
– Exothermic (H)
• energy of products lower than energy of reactants
– Endothermic (+
H)
• energy of products higher than energy of reactants
Energy Diagram
Exothermic Reaction
Energy Diagram
Endothermic
Catalysts
CATALYSTS HELP CHEMICAL
___________
REACTIONS _______________
HAPPEN FASTER
DECREASING the
Catalysts work by ____________
ACTIVATION ENERGY required
___________________________to
get a
chemical reaction started.
– NOTE:
– does not increase the amount of product
– does not get used up in the reaction
Enzymes
• Enzymes
– types of proteins
– act as biological catalysts
– speed up the rate of reaction in biological
processes (by lowering activation energy)
– most are specific to one reaction
Enzymes
• Naming Enzymes
• many end in _____
• beginning of the name tells what it does
• Examples:
• DNA Polymerase
• “polymerizes”
• joins monomers to make DNA
• Protease
• breaks down proteins
• ATP synthase
• synthesizes ATP
Energy Diagram
Enzymes
• Substrate
– reactants that bind to the enzyme
• Active Site
– location where the substrate binds on the enzyme
• Enzymes combine with the substrate in the
active site to form the enzyme-substrate
complex
Enzymes
• Lock & Key Model:
– substrate and active
site -> complimentary
shapes (puzzle pieces
that fit together)
• Enzymes exhibit
specificity:
– enzymes only fit with a
particular substrate
– due to the shape of the
active site
Enzyme Demonstration
5) Product Released;
enzyme free to react
again
1) Substrate
2) Fits into
active site
4) Reaction
takes place
3) Enzyme-Substrate
Complex
Enzymes
• Factors that affect enzyme activity
– pH
– temperature
– concentration (amt.) of substrate
– concentration (amt.) of enzyme
Enzymes
• Optimal pH
(dependent on
enzyme)
• Too low ->
decreased rate of
reaction
• Too high ->
enzyme
denatures
(breaks apart)
Denatured Proteins
• When a protein loses its shape (its tertiary (3-D)
structure)
• Cause:
-high temperature (like on the stove)
-pH extremes (like in your stomach)
• Effect:
-Losses its ability to function
-Properties can change
(become insoluble, change color)
Denatured Proteins
changesthe
• Denaturing an enzyme _______
_______
shape of the ______________
ACTIVE SITE so
enzyme
______________
____________
CAN’T BIND to SUBSTRATE
Denatured Proteins
• As a result, the reaction occurs at a
reduced rate or stops all together.
Enzymes
• Optimal Temp.
• Temp
,
Activity
• Temp too high->
protein
denatures
(breaks apart)
Enzymes
Predict what would happen if…
(1) you added more enzyme to the reaction?
(2) you added more substrate to the reaction?
WHITEBOARDS!
How does the amount of the substrate
and the amount of enzyme affect the
rate of reaction?
Lab: Understanding Enzymes
Objectives:
• Understand the function of enzymes in the
human body.
• Observe the function of several commercially
important enzymes.
• Predict the effect of enzyme concentration,
temperature, and pH on enzyme activity rate.
• Understand the structure of enzymes & how
denaturation occurs.
• Graph enzyme activity rates and different
enzyme concentrations.
Enzyme Inhibitors
• Competitive Inhibition
– plug up active site->substrate can’t bind
• Non-Competitive Inhibition
– bind to enzyme (not in active
site) --> change shape of
active site
Enzyme Inhibitors
• May be
– Permanent - covalent bond
– Reversible - hydrogen bond
• Examples
–
–
–
–
–
Nerve gas
Penicillin
Cyanide
Aspirin
AZT
Online Tutorials
for additional information & visuals
• http://resources.emb.gov.hk/biology/eng
lish/virtual_lab/flash/enzyme_lab.html
• http://www.bbc.co.uk/education/asguru/
biology/02biologicalmolecules/01protein
s/11enzymes/index.shtml
• http://www.tvdsb.on.ca/westmin/science
/sbi3a1/digest/enzymes.htm
Note: Not required.
Can you…
• …identify the parts of a chemical reaction?
• …relate energy changes to chemical
reactions?
– interpret energy diagrams?
• …summarize the importance of enzymes in
living things?
– enzymes (definition)?
– “lock and key” model?
– effect of temp. and pH on enzyme activity?