Controlling the level of glucose in the blood

UNDERSTANDING YOUR FOOD<br /> the ultimate educational resource<br /> TEACHER NOTES<br /> <br /> teachers’ notes S3.1<br /> S3. Controlling the level of glucose in the blood<br /> In this text-based activity pupils compare glucose and insulin levels<br /> recorded for a diabetic and a non-diabetic.<br /> Answers to questions on pupil<br /> sheet S3: Task 1<br /> 1. Graph<br /> 2. Rapidly reduces the level of blood glucose.<br /> Task 2<br /> 1. Rises steeply/quickly.<br /> 2. Eating a meal involves the digestion of food; this will increase the<br /> amount of glucose in the blood; this stimulates the production of<br /> KS4 science<br /> Timing - 20-25 minutes;<br /> possible homework exercise<br /> Two pupil activity sheets S3<br /> accompany this activity.<br /> Graph paper is needed<br /> 3. Returns to the original level (notto zero); it is important to note that<br /> there is a ‘background’ level of insulin in the bloodstream.<br /> 4. This is zero; this is not so in a ‘normal’ person.<br /> 5. It rises (but not as rapidly or to the same level as the ‘normal’ graph).<br /> 6. After an injection of insulin, there is a delay before it becomes ‘actively’<br /> present in the blood. Insulin is normally injected about half an hour<br /> before a meal. (There are now types available which can be injected<br /> just before eating.)<br /> 7. Zero; insulin-dependent diabetics cannot make their own insulin.<br /> ‘Normal’ people can make insulin and there is always some present in<br /> the bloodstream.<br /> <br /> pupil activity S3 CONTROLLING THE LEVEL OF GLUCOSE IN THE BLOOD<br /> The level of glucose in the blood is normally controlled by twohormones. These are<br /> calledinsulinandglucagon. Both of these are produced in thepancreas. This<br /> means that the pancreas has two different but very important functions. These are<br /> the production of digestiveenzymesand the production ofhormones.<br /> The parts of the pancreas that produce the hormones are called theIslets of<br /> Langerhans(islets - the tissue looked liked small islands; Langerhans- Paul Langerhans<br /> discovered this tissue).<br /> The control of blood sugar is an example of homeostasis (maintenance of a constant<br /> internal environment). Insulin and glucagon work in opposition to one another. Insulin<br /> works to remove excess glucose from the blood. Glucagon adds glucose to the<br /> blood in times of shortage.<br /> Insulinstimulates the conversion of glucose into a substance calledglycogen.<br /> Glycogen is a storagecarbohydrate. It is stored in theliverandmuscles. Insulin also<br /> stimulates the uptake of glucose by the cells of the body. Glucose is used in the<br /> process that produces energy, i.e. respiration. Insulin stimulates processes which have<br /> the effect ofloweringthe amount of glucose in the blood.<br /> Glucagonstimulates the conversion of glycogen from the liver into glucose. This has<br /> the opposite effect to insulin. This willincreasethe amount of glucose in the blood.<br /> Early onset diabetes(Insulin Dependant Diabetes, IDD) is a severe form of thecondition<br /> diabetes mellitus. In this condition there is a complete failure of the pancreas to<br /> produce insulin. If this is left entirely untreated it will be fatal. Patientssuffering from this<br /> form of the disease have to regularly monitor the level of glucose intheir blood. (The<br /> level of glucose in the blood is measured in millimoles per cubicdecimetre<br /> (mmol/dm<br /> 3<br /> )). In response to this patients have to have regular injections ofinsulin.<br /> Task 1<br /> The following questions show the effect that insulin has on the level of glucose in the<br /> blood of a 'normal' person.<br /> A person's level of blood glucose was measured. They were then given an injectionof<br /> insulin. The level of blood glucose was remeasured over time. The results are shown<br /> below.<br /> TIME LEVEL OF BLOOD GLUCOSE<br /> (minutes) (mmol/dm3)<br /> 0 4.1<br /> insulin injection15 4.1<br /> 30 1.9<br /> 40 3.8<br /> 60 3.8<br /> 90 3.9<br /> 120 4.2<br /> 1.Plot a line graph of these results. Put time along the bottom (x axis). Put the level<br /> of glucose (mmol/dm<br /> 3<br /> ) up the side (y axis).<br /> Remember to give your graph a title. Label the axes. Show where the injection of<br /> insulin was given.<br /> 2.What effect does insulin have on the level of glucose in the blood?<br /> <br /> CONTROLLING THE LEVEL OF GLUCOSE IN THE BLOOD pupil activity S3<br /> Task 2<br /> The following sketch graph shows the level ofinsulin(not glucose) in a 'normal' person.<br /> The graph shows what happens to this level after a meal has been eaten.<br /> The graph also shows the level of insulin in a diabetic in the same situation.<br /> The diabetic has been given an injection of insulin before the meal.<br /> Meal<br /> eaten<br /> Amount of<br /> insulin in blood<br /> Level of insulin<br /> in ‘normal’<br /> person<br /> Look at the 'normal'<br /> line.<br /> Time<br /> Level of insulin<br /> in a diabetic<br /> afterinjection<br /> of insulin<br /> before the<br /> meal<br /> 1.What happens to the amount of insulin in the blood when the meal is being eaten?<br /> 2.Why does eating a meal bring about this change?<br /> 3. What eventually happens to the amount of insulin?<br /> Look at the 'diabetic' line.<br /> 4.What is the level of insulin in the blood before the injection is given? In what way is<br /> this different to the 'normal' graph?<br /> 5.Describe what happens to the level of insulin in the blood following the injection.<br /> 6.Why should an injection of insulin be given about half an hour before a meal is<br /> eaten?<br /> 7. What is the level of insulin in the blood at the end of the graph? Explain this level.<br /> In what way is this different to the 'normal' graph?<br /> Insulin injected