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7Homeostasis and blood glucose exam practice questions Q1. (a) (i) What is meant by homeostasis? (1) (ii) Giving one example, explain why homeostasis is important in mammals. (2) (b) Cross-channel swimmers may suffer from muscle fatigue during which the contraction mechanism is disrupted. One factor thought to contribute to muscle fatigue is a decrease in the availability of calcium ions within muscle fibres. Explain how a decrease in the availability of calcium ions could disrupt the contraction mechanism in muscles. _ (3) (Total 6 marks) Q2. Diabetes is a disorder affecting the ability to control blood glucose concentration. One type of diabetes can be due to an abnormality of the insulin receptors in the cell surface membranes of cells in the liver and muscles. A high blood glucose concentration and the presence of glucose in the urine are signs of this type of diabetes. (a) (i) Suggest one way in which the insulin receptors might be abnormal. Do not bind to insulin (1) (ii) Explain how the presence of abnormal insulin receptors results in a high blood glucose concentration.
(iii) Explain how the kidneys normally prevent glucose appearing in the urine of a non-diabetic person. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ (3) (b) Twin studies have been used to determine the relative effects of genetic and Page 1 of 23
environmental factors on the development of this type of diabetes. The table shows the concordance (where both twins have the condition) in genetically identical and genetically non-identical twins. Concordance in genetically identical twins / % Concordance in genetically non- identical twins /% 85 35 (i) What do the data show about the relative effects of environmental and genetic factors on the development of diabetes? ______________________________________________________________ ______________________________________________________________ (1) (ii) Suggest two factors which should be taken into account when collecting the data in order to draw valid conclusions. 1. ____________________________________________________________ ______________________________________________________________ 2. ____________________________________________________________ ______________________________________________________________ (2) (Total 9 marks) Q3. Some mice have diabetes. The diabetes causes the blood glucose concentration to become very high after a meal. Scientists investigated the use of an inhibitor of amylase to treat diabetes. The scientists took 30 mice with diabetes and divided them into two groups, A and B Group A was given yoghurt without the inhibitor of amylase each day. Group B was given yoghurt with the inhibitor of amylase each day. Apart from the yoghurt, all of the mice were given the same food each day. The scientists measured the blood glucose concentration of each mouse, 1 hour after it had eaten. This was done on days 1, 10 and 20 after the investigation started. The following figure shows the scientists’ results. . Page 2 of 23
Days after the investigation started (a) Group A acted as a control in this investigation. Explain the purpose of this group.

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