Enzymes in depth:

If the temperature is too high, the enzyme’s active site denatures and the substrate can no longer fit into the active site. This reduces catalysed reactions.

If the pH of the enzyme is too high or low, it interferes with the bonds holding the enzyme together which denatures the active site. pH is usually a neutral 7, but not always.

The more enzymes there are in a solution, the more likely a substrate with meet with one and join. In summary, increasing the concentration of the enzyme increases the rate of reaction.

Investigating enzyme activity:

How does temperature affect enzyme activity?

Add a buffer solution with a different pH level to a series of different tubes containing the enzyme-substrate mixture.
Vary the initial concentrations of the substrate to investigate the effect of substrate concentration.
Vary the initial concentrations of the enzyme to investigate the effect of enzyme concentration.

How fast does a product appear?

The enzyme catalyse catalyses the breakdown of hydrogen peroxide into water and oxygen.
Collect the oxygen and measure how much is produced in a set time.
Use a pipette to add a set amount of hydrogen peroxide to a boiling tube. Put the tube in a water bath at 10 degrees Celsius.
Set up the rest of the apparatus with the source of catalase e.g. potato in a test tube full of hydrogen peroxide attached to a delivery tube which goes under the upside down measuring cylinder that is filled with water in a bowl of water. Use a water bath for constant temperature.
Record how much oxygen is produced in the first minute by counting bubbles that appear. Repeat three times and calculate a mean.
Repeat at 20-40 degrees Celsius.
Control variables = pH, potato used, size of potato etc.
Calculate the mean rate of reaction at each temperature. Mean rate of reaction = mean volume of oxygen produced/time taken.

How fast does a substrate disappear?

The enzyme amylase catalyses the breakdown of starch to maltose.
It is easy to detect starch using iodine solution - if starch is present, the iodine solution will change from browney-orange to blue-black.
Set up the apparatus with a starch solution + amylase solution in a water back. Every ten seconds, drop a sample of the mixture into a well using a pipette. When the iodine solution remains browney-orange, record the total time taken.
Repeat with the water bath at different temperature to investigate how it affects the time taken for the starch to be broken down.

	Created by Chloe Wood about 3 years ago

This is my revision, guided by a textbook, to a higher B1 exam.