Investigating 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.
Practice
- Check yourself: Investigating 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
In this experiment, we use the enzyme amylase and a starch solution. Amylase breaks down starch into maltose. We use iodine solution to test for starch.
Every thirty seconds, we put a drop of the mixture into iodine. While starch is present, the iodine turns blue black. When the starch has gone, the iodine stays orange brown.
First, we test temperature. We use water baths at ten, thirty seven, and sixty degrees Celsius. We change only the temperature. We keep the volume, the concentration, and the P H the same, so it is a fair test.
We measure the time until the iodine stops turning blue black. The shortest time means the fastest rate. At thirty seven degrees, it is fastest. At sixty degrees, the enzyme is denatured, so the starch stays.
Now we test P H. We use buffer solutions, which keep the P H steady. We try P H three, P H seven, and P H eleven. Everything else stays the same.
Again, we measure the time. The rate is fastest at the optimum P H, here about seven. At a very low P H, the enzyme is denatured. At a high P H, it works slowly.
Remember. Amylase breaks down starch, and iodine tests for starch. Change only one variable. The shortest time means the fastest rate. And too hot, or the wrong P H, means no reaction.
More in this series
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1:41What are enzymes?
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1:40How enzymes work
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2:14Enzymes: 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.
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.