Enzymes - Practical Work


Enzyme investigations

Expected to investigate the effect of temperature, pH, substrate and enzyme concentration on enzyme activity. It is important to ensure that all the appropriate variables are controlled when carrying out enzyme experiments. E.g. if you are measuring the effect of temperature on a specific enzyme activity, it is important to make sure that other factors such as enzyme and substrate concentration and pH are controlled.

Illustration of enzyme immobilisation

Immobilisation of lactase in alginate beads - milk initially has no affect on a Clinistix ***** but after passing through a column of alginate beads (with immobilised lactase), the Clinistix test becomes positive. This can be explained by the lactose in the milk being broken down to its monosaccharide constituents, glucose and galactose. The presence of glucose causes the colour change in the Clinistix.

Using a colorimeter

A colorimeter is a piece of apparatus that measures the change in intensity of light as it passes though a solution.

Colorimeters can record the amount of light that is absorbed (absorbance) by the solution or the amount of light that passes through (transmission). 

It is important to calibrate the colorimeter. For example, if the colorimeter is going to follow the course of amylase breaking down starch to maltose, a weak solution of iodine could be calibrated as the end point or 'blank', ie 100% transmission.

An appropriate filter is used that will maximise the change in transmission/absorbance as the investigation progresses (provides…


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