MAINTAINING A BALANCE
HSC CourseCore Topic 1
- Factors Affecting Activity of Enzymes
Enzyme activityHow fast an enzyme is working = Rate of Reaction
Rate of Reaction = Amount of substrate changed (or amount product formed)
in a given period of time.
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Enzyme activity
Variable you are looking at
Factors Affecting Enzyme Activity
Temperature pH Substrate concentration Presence of activators
Coenzymes Cofactors
Presence of enzyme inhibitors
TemperatureThe effect: Most enzymes work
best at certain temperatures i.e. 370C in mammals.
The speed of the reaction decreases if the temperature varies from this level.
The activity of most enzymes increases as temperature increase.
Why does it happen?
Increased temperaturecauses molecules to
move more rapidly which in
turn causes more collisions between molecules.
This increases the chances
of the substrate colliding
with the enzyme’s active
site.
Denaturing If the temperature
rises above a certain level, the enzyme denatures (changes it shape so its active site is no longer correctly exposed) to become inactive and can no longer bind with the substrate.
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Temperature
0 20 30 5010 40 60
40oC - denatures
5- 40oC Increase in Activity
<5oC - inactive
Each enzyme has it own optimal temperature. The hydrogen bonds holding proteins together are broken by high temperatures and this disrupts their three dimensional shape.
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pH
1 3 42 5 6 7 8 9
pH
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1 3 42 5 6 7 8 9
Narrow pH optima
pH
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1 3 42 5 6 7 8 9
Narrow pH optima
WHY?
pH
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pH
1 3 42 5 6 7 8 9
Narrow pH optima
Outside this range also disrupt bonding of protein molecule Changes structure/shape and therefore alters the active site.
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Enzyme Concentration
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Enzyme Concentration
Enzyme Concentration
As enzyme concentration increses, rate of reaction increases.
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Substrate Concentration
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Substrate Concentration
Substrate Concentration
As substrate concentration increases, reaction rate increases until all active sites are filled. After this point, the reaction plateaus and can not proceed any faster. This point is called enzyme saturation point.
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Substrate Concentration
Substrate Concentration
Active sites full- maximum turnover
Presence of Activators
Coenzymes and Cofactors
Coenzymes – Organic molecules that may be required for enzyme activity
Cofactors – Inorganic molecules that may be required for enzyme activity
Presence of Enzyme Inhibitors
Other molecules that block the active site of enzymes. The stop the substrate from binding to the active site.