Testing Urine (WJEC GCSE Biology)

Testing urine

• Urine can be analysed to quickly test for diseases such as diabetes or kidney disease
• In this practical artificial urine is tested for glucose or protein or both
  • You are not expected to test real urine samples for safety reasons
  • Your samples may be dyed to resemble real urine more closely
    • Colour can be an important factor because it may affect your ability to determine other colour changes during the testing process
• You will be given unknown samples of artificial urine and asked to test them; the purpose here is to diagnose the simulated 'patients' with different health conditions

Test for glucose 

• Testing urine for glucose can be an indicator of diabetes
• To carry out the test:
  1. Add Benedict's solution to the sample solution in a test tube
  2. Heat in a boiling water bath for 5 minutes
  3. Take the test tube out of the water bath and observe the colour
  4. A positive test will show a colour change from blue/green to orange/brick red
     • Note that Benedict's solution would normally be blue, but may appear green here due to the existing yellow colour of the sample

Benedict's test for glucose diagram

The glucose test involves boiling a test solution with Benedict's solution and observing any colour change

Test for protein

• Testing urine for protein can indicate kidney disease
• To carry out the test:
  1. Add drops of Biuret solution to the food sample
  2. A positive test will show a colour change from blue/green to lilac/purple/light green
     • Note that Biuret solution would normally be blue, but may appear green here due to the existing yellow colour of the sample
     • The yellow sample colour may also mean that a positive result will be a different shade of green rather than lilac

Biuret test for protein diagram

The Biuret test can be used to test urine for the presence of protein

Results

• A set of sample results from the investigation described might be as follows:

Results of artificial urine testing table

Sample from 'patient'	Biuret test observation	Protein present/absent	Benedict's test observations	Glucose present/absent
A	Lilac	Present	Blue	Absent
B	Blue	Absent	Brick red	Present
C	Blue	Absent	Blue	Absent
D	Lilac	Present	Brick red	Present

• The following conclusions could be drawn from these results: 
  • Patient A = protein but not glucose, indicating kidney disease
  • Patient B =glucose but not protein, indicating diabetes
  • Patient C = neither glucose nor protein, indicating no disease
  • Patient D = both protein and glucose, indicating both kidney disease and diabetes

Risk assessment

• A hazard in an experiment is something that could potentially harm you
• A risk is the harm that could occur as a result of the risk
• A control measure is the action taken to reduce the chance of the hazard causing a problem

Testing artificial urine risk assessment table

Hazard	Risk	Control measure
Biuret is an irritant	Biuret solution could spill onto the skin or get into the eyes	Wash hands if contact is made Wear gloves to prevent contact with skin Wear safety goggles
Hot water	Scalding could occur if hot water touches the eyes / skin when moving samples in/out of the water bath	Wear safety goggles and use test tube holders to transfer tubes in/out of water bath