1.10: how pH affects enzyme activity core practical

What is the purpose of this core practical?

To determine which pH is optimum for enzyme activity

What is the method?

Set a Bunsen burner up with a heatproof mat, gauze and a tripod. Place a beaker of water on the gauze and maintain a temperature of 35 degrees C in the water. Add two drops of iodine solution into each spot of a spotting tile. Add 2cm³ of amylase solution and 2cm³ of starch solution to a test tube then add 1cm³ of pH solution to the tube (to keep the pH constant). Mix and place into the beaker of water on the Bunsen burner. Use a pipette to remove a few drops of solution and put them into a different well of the spotting tile. Repeat until the iodine solution stops turning black. Repeat with other pH solutions.

What risks are involved?

Iodine solution is an irritant, so wash off skin. Wear goggles at all times. When the Bunsen burner is not in use, keep the flame orange (safety flame)

Why is the water kept at 35 degrees?

This is close to body temperature, so the enzyme activity will be close to as it is in the body

What would happen to the enzyme reactivity if the temperature was lower?

The reactivity would decrease

What would happen to enzyme activity if the temperature was increased?

The enzymes would start to denature so the activity would decrease

What is the optimum pH of amylase?

7

How can you tell what the optimum pH is?

It is the shortest time taken before the iodine changed colour - this shows that the starch was broken down more quickly (a faster rate of reaction)