Enzymes: Effects Of Temperature And pH
5.2 Effects Of Temperature And pH On Enzyme Activity
Progress Of Enzyme-Catalysed Reactions
- Followed by measuring substrate decrease or product increase.
- Example: starch breakdown measured using iodine test.
Effect Of Temperature
- Low temperature → molecules have less kinetic energy → fewer collisions.
- Optimum temperature → maximum enzyme activity.
- High temperature → enzyme denatures (active site shape destroyed, irreversible).
Graph Shape:
- Increases steadily until optimum.
- Sharp fall after denaturation.
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Effect Of pH
- Each enzyme has an optimum pH (most enzymes work best near neutral pH 7, pepsin works best in acidic pH).
- pH too low/high → changes shape of active site → denaturation.
Key Terms
- Optimum temperature/pH: conditions where enzyme works fastest.
- Denaturation: permanent loss of enzyme activity due to change in active site shape.
- Effective collisions: successful substrate-enzyme interactions.
Examples
- Amylase → optimum around pH 7.
- Pepsin (stomach enzyme) → optimum around pH 2.
- Trypsin (small intestine) → optimum around pH 8.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course