Enzymes – heroes and villains
Because of their high sensitivity and specificity, enzymes may be used as analytical reagents. The use of glucose oxidase and peroxidase in testing for glucose.
Enzymes are becoming more and more widely used in medicine. Enzymes are highly specific and sensitive to change. Enzymes can be used as analytical reagents – analytical agents are used to analyse (discover) what is in a substance or mixture and/or its concentration. The example that AQA refers to is the test for glucose – glucose in the urine is a classic test for diabetes. If glucose can be detected in the urine effectively then the patient can undergo further treatment. It is a classic example of an analytical tool.
So how does the glucose oxidase and peroxidase test for glucose in the urine?
We have established that urine of a person with diabetes may contain glucose. If the urine is tested with two enzymes, glucose oxidase and peroxidase the following reactions can be detected.
Glucose + oxygen ——> gluconic acid + hydrogen peroxide
The chemical Chromagen is also used. This is normally colourless. Peroxidase breaks down the hydrogen peroxide. The chromatin dye is then oxidised and become colourless.
colourless chromagen + hydrogen peroxide — peroxidase enzyme –> coloured chromagen + water
This test uses a glucose test strip. The strips contain the two enzymes and the Chromagen. The colour change indicates the level of urine change. More information
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