Blood glucose regulation

Type 1 diabetes mellitus is characterised by a lack of insulin production. Type 2 diabetes mellitus can involve reduced production of insulin and a decreased response to insulin.

* Scientists analysed the occurrence of diabetes in identical and non-identical twins.

Identical twins have the same DNA. Non-identical twins share approximately 50% of each other’s DNA.

The scientists selected 614 pairs of twins in which at least one of the individuals had diabetes: 109 pairs had type 1 diabetes; 505 pairs had type 2 diabetes.

The scientists calculated the percentage probability of an individual having diabetes when their twin has the disease.

The table shows the percentage probability of both individuals in a pair of twins developing either type 1 or type 2 diabetes.

Explain what conclusions can be drawn from the data in the table about the influence of the environment and genetics on the probability of developing diabetes.

Extra answer space if required.

Insulin is secreted from cells in the pancreas.

This is a photomicrograph of pancreatic tissue.

Identify the structures labelled A, B and C.

The graph shows the changes in the rate of insulin secretion in a person with type 2 diabetes after consuming glucose.

The table shows the changes in the rate of insulin secretion in a person with normal glucose tolerance after consuming glucose.

Plot the data from the table on the graph and draw a line of best fit.

The table lists statements about a molecule of insulin.

Complete the table by stating the level of protein structure (primary, secondary, tertiary or quaternary) to which the statement relates.

Bacteria can be genetically modified to produce insulin.

State how a plasmid containing the gene coding for insulin can be transferred into a bacterial cell.

Suggest how bacterial cells can be screened to check if they have taken up a recombinant plasmid.

In the future, type 1 diabetes could be treated by giving patients new pancreatic -cells that have been produced in a laboratory from stem cells.

State a feature of stem cells that allows them to be used to produce pancreatic -cells.

Future treatments for type 1 diabetes may be able to use stem cells from a patient’s body to produce new -cells.

Explain why patients receiving these new -cells would still need to be given immunosuppressant drugs.

Glands can be either endocrine or exocrine.

Describe what is meant by an endocrine gland.

The pancreas contains endocrine glands such as the Islets of Langerhans. It also contains cells that produce digestive enzymes.

Suggest why the cells that produce digestive enzymes are described as exocrine rather than endocrine.

Hormones can be classed as either steroid or non-steroid. Steroids are lipid soluble.

Suggest the location of the receptors for steroid hormones and state a reason for your suggestion.

The Society for Endocrinology has produced a booklet about adrenal failure to help patients understand their illness.

The following statements are adapted from this booklet.

• Adrenal failure is caused by inability of the adrenal glands to produce sufficient amounts of cortisol and aldosterone.

• In healthy people, the hormone ACTH is produced by the pituitary gland and causes the adrenal cortex to release more cortisol and aldosterone.

• A pituitary tumour can stop ACTH production by the pituitary. This leads to adrenal failure.

• Symptoms of adrenal failure include severe fatigue and weakness, weight loss, low blood pressure and salt craving.

Explain the symptoms of adrenal failure.

Explain why patients with a pituitary tumour have adrenal failure but still respond normally to situations of danger or excitement.

Hypothyroidism (underactive thyroid gland) is treated by taking thyroxine tablets.

Scientists are investigating the use of stem cell transplants to treat hypothyroidism in which the thyroid glands of mice are destroyed using radioactive iodine.

The scientists obtained mouse embryonic stem cells (ESCs) and incubated them in culture with or without a mixture of growth factors for 30 days before transplanting them into the mice.

They divided the mice into four groups as shown in the table.

After eight weeks they measured the thyroxine concentration in the four groups of mice. Their results are shown in the graph. Each cross represents a single mouse and the mean ± 2 standard deviations is shown for each group.

The ESCs are described as pluripotent. Explain what is meant by pluripotent.

The scientists concluded that growing the ESCs with growth factors caused them to differentiate into functional thyroid tissue.

Evaluate this conclusion.

The scientists then repeated their experiments with adult stem cells taken from the skin of patients with hypothyroidism. These cells were artificially transformed into pluripotent stem cells (iPSCs).

The scientists concluded that use of human iPSCs would be safer than using human ESCs to treat hypothyroidism.

Use your knowledge of stem cells to suggest one reason that supports and one reason that does not support the scientists’ conclusion.

Which of the statements about the control of blood glucose is correct?

A Pancreas cells increase their release of glucagon when blood glucose concentration rises above a set level.

B Glucagon stimulates the conversion of glycogen to glucose by liver cells.

C Insulin increases blood glucose concentration by stimulating glycogenesis gluconeogenesis.

D The interaction of insulin and glucagon keeps the blood glucose concentration constant.

The pancreas produces digestive enzymes and is also involved in the regulation of blood glucose concentration.

Fig. 17, in the insert, shows a light micrograph of a section of mouse pancreas.

Identify the structures labelled K and L in Fig. 17.

Scientists investigated the effect of the drug nifedipine on the secretion of insulin from pancreas cells in culture.

Pancreas cells were first incubated with glucose at a concentration of 3 mmol dm^–3. The concentration of glucose was then increased to 20 mmol dm^–3 in the presence or absence of nifedipine.

The scientists then measured the amount of insulin secreted by the cells. They recorded their results as a percentage of the total insulin content of the cells. Each experiment was repeated seven times.

The results are shown in the table.

Name the cells that secrete insulin.

Explain why it was necessary to increase the concentration of glucose surrounding the cells before they measured insulin secretion.

Suggest and explain which statistical test the researchers would have used to analyse their data.

The statistical test gave a value of p < 0.001. Use the words ‘chance’ and ‘probability’ to draw a conclusion from the result of the statistical test.

Nifedipine blocks Ca²⁺-channels. (v)

Explain how blocking calcium channels could inhibit insulin secretion.

* Type 1 diabetes has been treatable for many years, but treatments are always improving.

Evaluate the treatments for type 1 diabetes that have been used in the past as well as current and potential future treatments.

Additional answer space if required.

Banting and Best pioneered experiments into the functions of the pancreas.

In one experiment, they removed the pancreas of dogs. Shortly afterwards, the dogs developed the symptoms of diabetes.

• Banting ground up the removed pancreas to produce an extract.

• He called the extract “isletin”.

• The isletin was then injected into dogs that had had their pancreas removed.

• He then tested the blood glucose concentration.

The graph below is a summary of the results.

Which of the following statements correctly explains these results?

1 Isletin is made in the cells in the islets of Langerhans. 2 Isletin reduces blood glucose concentration. 3 The effects of isletin are short-lived.

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Your answer

Gestational diabetes is a medical condition that affects pregnant women. It results in high levels of glucose in the blood, even though the woman produces normal levels of insulin.

Gestational diabetes is most similar to which other type of diabetes?

Explain your answer.

Suggest two ways a woman with gestational diabetes can manage her condition.

Skeletal muscle is one of the main tissues where glucose is removed from the blood in response to insulin.

Name the other tissue.

Explain why glucose is required for the contraction of skeletal muscle.

During late pregnancy, women find ventilation more difficult, as the developing foetus reduces the volume of the thorax. This can lead to tiredness and difficulty breathing.

A student used a spirometer to measure ventilation in a woman who was 36 weeks pregnant.

Fig. 16.1 shows the trace produced.

Mean oxygen uptake rate at rest in women is around 0.020 dm³ s^–1.

Using these data, the student made the following conclusion:

My data show that being pregnant reduces rate of oxygen uptake by up to 20%.

Evaluate this claim, using the data in Fig. 16.1.