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Biology journal Cambridge IGCSE 0610

Enzymes · 3 parts · syllabus 5.1

What temperature does an enzyme work best at?

Mix amylase with starch in a water bath and put a drop of the mixture onto iodine every 30 seconds until the starch has gone. Time it at six temperatures and three pH values, work out relative rates, and look inside the mixture at the active sites.

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Two bowls of pineapple jelly: the one made with tinned pineapple has set firm, the one made with fresh pineapple is still runny. (enlarge)

Follow the idea

  1. Catalysts in living things

    Catalysts and enzymes: the active site, the enzyme–substrate complex and why each enzyme has one job

    Not started

  2. Temperature and enzymes

    Timing amylase at different temperatures: optimum temperature, collisions and denaturation

    Not started

  3. pH and enzymes

    Amylase at different pH values: buffers, optimum pH and the shape of the active site

    Not started
A water bath on a hotplate holding two test tubes and a thermometer; in front, a spotting tile with rows of wells going from blue-black to orange-brown, one row all blue-black; an amber iodine bottle, a dropping pipette and a stop-clock.

The experiment · Amylase and starch on iodine · time the end point at six temperatures and three pH values

Run it yourself, or project it for the class

Use the apparatus step by step and look closely at what happens. The whole experiment fits one screen, so it works on a projector too.

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