Download Enzyme Activity

Enzyme Activity
Turnip Peroxidase
Guaiacol
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Tetraguaiacol
Guaiacol
 Absorbance

AP Biology
Increases as reaction occurs
Enzyme Activity
 Graph data
 What are you changing?
Time
 (IV)

What is the response?
•Change in absorbance
•(DV)
How do you graph the data?
•Absorbance vs time
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Measuring Rates of Reaction
 Graph absorbance vs time
 Determine slope of increase
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Enzyme Activity vs Temperature:
 Explain the graph.



Where does denaturation fit into the graph?
If another enzyme from a north sea crustacean was
studied and its enzyme activity was plotted on the
graph, where would it appear?
If a hot springs bacterial enzyme was studied and
its activity data was plotted, where would it lie?
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Rxn Rate vs Enzyme Concentration
 Explain the graph.

Why is the reaction rate linear and not curved?
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Rxn Rate vs Substrate Concentration
 Explain the graph
 Why does it differ from the graph of


Reaction Rate vs Enzyme Concentration
When was the rate the highest, and why?
When was the rate the slowest, and why?
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Rate of Reaction
Enzyme-Mediated Reaction:
Moles of Product Produced vs Time.
Which graph below-right summarizes the rate of the
reaction depicted by the Moles of Product Produced vs
Time graph?
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Lock and Key model
 Simplistic model of enzyme
action

substrate fits into 3-D
structure of enzyme’ active
site
 H bonds between substrate &
enzyme


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like “key fits into lock”
specificity
In biology…
Shape matters!
Induced fit model
 More accurate model of enzyme action
3-D structure of enzyme fits substrate
 substrate binding cause enzyme to
change shape leading to a tighter fit

 “conformational change”
 bring chemical groups in position to catalyze
reaction
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How does it work?
 Variety of mechanisms to:
lower activation energy & speed up
reaction

synthesis
 active site orients substrates in correct position
for reaction
 enzyme brings substrate closer together

digestion
 active site binds substrate & puts stress on bonds
that must be broken, making it easier to separate
molecules
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Factors Affecting Enzyme Fxn
 Enzyme concentration
 Substrate concentration
 Temperature
 pH
 Salinity
 Activators
 Inhibitors
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catalase
Factors affecting enzyme fxn:
Enzyme Concentration
 Enzyme concentration

as  enzyme =  reaction rate
 more enzymes = more frequently collide with
substrate

reaction rate levels off
reaction rate
 substrate becomes limiting factor
 not all enzyme molecules can find substrate
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enzyme concentration
Factors affecting enzyme fxn:
Substrate Concentration
 Substrate concentration

as  substrate =  reaction rate
 more substrate = more frequently collide with
enzyme

reaction rate levels off
reaction rate
 all enzymes have active site engaged
 enzyme is saturated
 maximum rate of reaction
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substrate concentration
Factors affecting enzyme fxn:
Temperature
 Temperature

Optimum T°
 greatest number of molecular collisions
 human enzymes = 35°- 40°C
 body temp = 37°C

Heat: increase beyond optimum T°
 increased energy level of molecules disrupts
bonds in enzyme & between enzyme & substrate
 H, ionic = weak bonds
 denaturation = lose 3D shape (3° structure)
Cold: decrease T°
 molecules move slower
 decrease collisions between enzyme & substrate
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
Enzymes and temperature
 Different enzymes function in different
organisms in different environments
reaction rate
human enzyme
hot spring
bacteria enzyme
37°C
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temperature
70°C
(158°F)
Factors affecting enzyme fxn:
SALINITY
 Salt concentration

changes in salinity
 adds or removes cations (+) & anions (–)
 disrupts bonds, disrupts 3D shape
 disrupts attractions between charged amino acids
 affect 2° & 3° structure
 denatures protein

enzymes intolerant of extreme salinity
 Dead Sea is called dead for a reason!
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Factors affecting enzyme fxn:
pH
 pH

changes in pH
 adds or remove H+
 disrupts bonds, disrupts 3D shape
 disrupts attractions between charged amino acids
 affect 2° & 3° structure
 denatures protein

optimal pH?
 most human enzymes = pH 6-8
 depends on localized conditions
 pepsin (stomach) = pH 2-3
 trypsin (small intestines) = pH 8
0 1 2 3 4 5 6 7 8 9 10 11
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