How temperature and pH change enzyme activity, rate = 1000 ÷ time, the amylase and pH required practical and the food tests.
What you will learn
- Explain the effect of temperature and pH on enzymes, including denaturing
- Calculate rates with rate = 1000 ÷ time and find an optimum
- Plan and analyse the amylase practical
- Use iodine, Benedict's, Biuret and the emulsion test
Temperature, pH and denaturing
Warming an enzyme and its substrate makes the molecules move faster, so they collide more often and the rate rises.
Above the optimum the bonds holding the enzyme's shape break, the active site changes shape and the substrate no longer fits: the enzyme is denatured, and that is permanent.
pH works the same way: far from its optimum pH the active site changes shape. Most human enzymes work best near 37 °C and pH 7; pepsin in the stomach works best near pH 2.
The rate falls above the optimum because the enzyme is denatured, not because it is killed or used up.
The rest of this lesson and its 13 practice questions are locked.
In this lesson
- Temperature, pH and denaturing
- Required practical: amylase and pH
- Required practical: food tests
- Try it: A rate from a time
13 practice questions, marked as you go; about 25 minutes in all.
Key terms
Optimum
In this unit: Organisation: tissues, organs, digestion and circulation
Levels of organisation, digestion and enzymes with the amylase and food test practicals, the heart, blood and lungs, heart disease and cancer, and transport in plants.
- Organisation, digestion and enzymes
- Enzyme activity and the food tests
- The heart, blood vessels and blood
- The lungs and gas exchange
- Heart disease, risk factors and cancer
- Plant tissues and transport
- Health, lifestyle and body measurements
- Cancer: tumours, risk factors and data
All of Organisation: tissues, organs, digestion and circulation