Enzymes: temperature and pH
Why a higher temperature speeds up an enzyme, what the optimum is, and how heat or the wrong pH changes the shape of the active site (denaturation). With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.
Practice
- Check yourself: Enzymes: temperature and pH – Type the missing words, put the steps in order and write a short answer. No multiple choice: you have to remember it. Vietnamese help for every question.
Transcript
What happens when the temperature goes up? Molecules gain kinetic energy. This means they move faster.
Enzyme and substrate molecules collide more often. There are more effective collisions, so more enzyme substrate complexes form, and the rate of reaction goes up.
As the temperature rises, the rate keeps increasing, until the optimum temperature. For human enzymes, this is about thirty seven degrees Celsius.
Above the optimum, the enzyme starts to change shape. The active site is no longer complementary to the substrate. The enzyme is denatured, and the reaction stops. This change is permanent.
Enzymes also have an optimum P H. At the optimum P H, the enzyme works fastest.
If the P H is too high or too low, the shape of the active site changes. The substrate no longer fits, and the enzyme is denatured.
Different enzymes have different optimum P H values. Pepsin, in the acid stomach, works best at about P H two. Amylase, in saliva, works best at about P H seven.
Remember. A higher temperature means more kinetic energy and more collisions. The rate is fastest at the optimum temperature and P H. If it is too hot, or the P H is wrong, the enzyme changes shape and is denatured.
More in this series
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Twelve key words for IGCSE Co-ordinated Sciences topic B4, with the Vietnamese meaning, how to say each word, a picture and an example. Ends with a test section, and a typing trainer on the site.
1:41What are enzymes?
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1:40How enzymes work
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2:16Investigating enzymes: temperature and pH
A practical with amylase, starch and iodine on a spotting tile: how to test the effect of temperature and pH, keep it a fair test and read the results. With Vietnamese subtitles. A “Check yourself” section with typed questions is below the video on the site.
5:30B4 quiz: enzymes
Ten think-time questions on enzymes: catalysts, the active site, specificity, temperature, pH and the amylase practical. Below the video: written workbook questions with model answers.