Diagnosis of diabetes mellitus

UNDERSTANDING YOUR FOOD<br /> the ultimate educational resource<br /> TEACHER NOTES<br /> <br /> teachers’ notes S2.1<br /> S2. Diagnosis of diabetes mellitus<br /> Pupils test samples of ‘urine’ with Benedict’s solution and Clinistix.<br /> You will find that tube B will not clean after the test has been carried out;<br /> a small amount of bench HCl added to the tube will remove the orange<br /> colour.<br /> Answers to questions on pupil sheet S2:<br /> 1. only sample B<br /> 2. sample B<br /> 3. The information from the second paragraph will help pupils form an<br /> answer.<br /> .<br /> KS3 and KS4<br /> science<br /> Timing - 30 - 40 minutes<br /> Pupil activity sheet S2 accompanies<br /> this activity.<br /> Requirements<br /> • 3 samples of ‘urine’:<br /> water + food colouring - labelled A<br /> water + glucose + food colouring -<br /> labelled B<br /> water + food colouring - labelled C<br /> (the food colouring is to make<br /> the liquids look realistic!)<br /> • Benedict’s reagent<br /> • test tubes or boiling tubes<br /> • test tube holder<br /> • test tube rack<br /> • water bath (beaker of water<br /> heated over Bunsen flame)<br /> • safety goggles<br /> • stop clocks<br /> • Clinistix - available from<br /> pharmacists follow the instructions<br /> on the pack very carefully)<br /> <br /> DIAGNOSIS OF THE DISEASE DIABETES MELLITUS pupil activity S2<br /> The presence ofglucosein the urine is one of the signs that a person may be<br /> suffering from diabetes.<br /> There is a normal amount of glucose contained within the blood. When this blood is<br /> filtered as it passes through the kidney, all of the glucose is reabsorbed back into the<br /> bloodstream. This means that under normal circumstances glucose should not be<br /> present in the urine. However, in a person suffering from diabetes there is an<br /> abnormally high level of glucose in the blood. As this blood passes through the<br /> kidneys not all of the glucose can be returned to the blood. Hence, some of it will be<br /> present in the urine.<br /> It is quite easy to test for the presence of glucose in a liquid such as urine. Glucose is<br /> an example of areducing sugar. It can be detected using a test called the<br /> Benedict's test.<br /> An unknown sample of liquid is boiled withBenedict's solution. If anorange-red<br /> precipitate appears then the unknown sample does contain glucose. This is apositive<br /> result.<br /> You are given three samples of 'urine' labelled A - C (it is not real urine!). Carry out the<br /> following test on small samples of each 'urine'. Each test must be carried out in a<br /> separate test tube.<br /> SAFETY NOTE<br /> REMEMBER TO WEAR GOGGLES<br /> 1.Pour about 2 cm depth of 'urine' into a test tube.<br /> 2.Add an equal depth of Benedict's solution. This is abluesolution.<br /> 3.Place the tube in a boiling water bath.<br /> 4.After about 60 - 90 seconds record the colour of the mixture in the tube.<br /> 5.Repeat the test with the other samples.<br /> Questions<br /> 1.Which of the samples contained glucose?<br /> 2.Which of the samples could be from a person suffering from diabetes?<br /> 3.Imagine you were the doctor carrying out similar tests. How would you explain<br /> simply the presence of glucose in the urine to the patient whose urine you had<br /> tested?<br /> Doctors do not usually carry out a Benedict's test in their surgeries. Instead, they can<br /> carry out a test which takes just a few seconds. This test uses a special piece of<br /> equipment called a Clinistix. If these are available you could use them to confirm the<br /> results from your Benedict's tests.