enzyme activity - the bronx high school of science · ap biology enzyme activity vs temperature:...
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AP Biology
Guaiacol
Tetraguaiacol
Enzyme Activity
Turnip Peroxidase
AP Biology
Guaiacol Absorbance
Increases as reaction occurs
AP Biology
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
AP Biology
Measuring Rates of Reaction
Graph absorbance vs time
Determine slope of increase
AP Biology
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?
AP Biology
Rxn Rate vs Enzyme Concentration
Explain the graph.
Why is the reaction rate linear and not curved?
AP Biology
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?
AP Biology
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?
AP Biology
Lock and Key model Simplistic model of enzyme
action
substrate fits into 3-D structure of enzyme’ active site H bonds between substrate &
enzyme
like “key fits into lock”
specificity
In biology… Shape matters!
AP Biology
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
AP Biology
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
AP Biology
Factors Affecting Enzyme Fxn
Enzyme concentration
Substrate concentration
Temperature
pH
Salinity
Activators
Inhibitors
catalase
AP Biology
Factors affecting enzyme fxn: Enzyme Concentration
Enzyme concentration
as enzyme = reaction rate more enzymes = more frequently collide with
substrate
reaction rate levels off substrate becomes limiting factor
not all enzyme molecules can find substrate
enzyme concentration
reac
tio
n r
ate
AP Biology
Factors affecting enzyme fxn: Substrate Concentration
substrate concentration
reac
tio
n r
ate
Substrate concentration
as substrate = reaction rate more substrate = more frequently collide with
enzyme
reaction rate levels off all enzymes have active site engaged
enzyme is saturated
maximum rate of reaction
AP Biology
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
Factors affecting enzyme fxn: Temperature
AP Biology
Enzymes and temperature
Different enzymes function in different
organisms in different environments
37°C temperature
rea
cti
on
rate
70°C
human enzyme hot spring
bacteria enzyme
(158°F)
AP Biology
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!
AP Biology
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 7 2 0 1 3 4 5 6 8 9 10 11
Factors affecting enzyme fxn: pH