Blood glucose regulation

What term is used to describe the maintenance of a stable internal environment?

A high blood glucose concentration can cause dehydration of body cells.

Explain why.

Do not refer to ADH or the role of the kidneys in your answer.

The hormone glucagon is involved in maintaining a stable blood glucose concentration.

Which is not a result of the action of glucagon?

Tick (✓) one box.

Figure 1 shows one of the physiological systems involved in controlling blood pH.

Use the information in Figure 1 to outline the principles of negative feedback.

Vigorous exercise causes a change in blood pH and in the rate of ventilation.

Use Figure 1 to describe and explain these changes.

A person with diabetes is in diabetes remission if their blood glucose concentration is below the diabetes threshold concentration for at least 3 months. This diabetes remission is achieved without taking medication.

Scientists investigated whether a weight-loss programme would result in type II diabetes remission.

The scientists:

• used a computer-generated list to select 380 volunteers from a large number of health centres

• selected volunteers aged 25 to 60 years, each with less than 5 years duration of type II diabetes

• divided the volunteers in the ratio 1: 1 between experimental group P and control group Q

• placed group P on a weight-loss programme for the 2-year duration of this investigation

• recorded loss of mass and percentage of volunteers in each group in type II diabetes remission after 2 years.

Give two reasons why a weight-loss programme could be used to treat type II diabetes but not type I diabetes.

The design of this investigation helps to support the validity of any conclusions obtained.

Suggest and explain three features of this investigation that justify this statement.

Table 3 shows some of the scientists’ results.

Use the information provided to calculate the difference in number of volunteers between the two groups who achieved diabetes remission.

Show your working.

Use all the information to evaluate whether a weight-loss programme is an effective treatment for type II diabetes.

Scientists investigated the production of laboratory rats with the characteristics of type II diabetes. The scientists used the following method.

• They divided the rats into two groups, A and B, and fed them different diets for 2 weeks.

• They fed the rats in group A the normal diet containing 12% fat.

• They fed the rats in group B a high-fat diet containing 56% fat.

• After 2 weeks, they injected both groups of rats with 35 mg kg^–1 of the drug streptozotocin (STZ) to induce diabetes.

1 week later, the scientists determined the mean body mass and mean blood glucose concentration for each group.

Table 3 shows the results.

Table 3

A value of ± 2 × SD from the mean includes over 95% of the data.

Calculate how many grams of STZ should be injected into a rat with a mass of 230.45 g. Show your working.

Give your answer in standard form.

Suggest and explain why STZ was injected per unit of body mass.

The scientists concluded that group B rats could be used for studying type II diabetes in humans.

Use all the information and your knowledge of type II diabetes to evaluate this conclusion.

The scientists repeated the investigation using much higher doses of STZ. This led to destruction of pancreatic cells. The scientists concluded that these rats would not be suitable for studying type II diabetes.

Give two reasons why the scientists made this conclusion.

Neonatal diabetes is a disease that affects newly born children. The disease is caused by a change in the amino acid sequence of insulin.

This change prevents insulin binding to its receptor. Explain why this change prevents insulin binding to its receptor.

Phosphoinositide 3-kinase (PI3K) is an enzyme in several metabolic processes.

Figure 5 shows the role of PI3K in the control of blood glucose concentration.

A decrease in the activity of PI3K can cause type II diabetes.

Use Figure 5 to explain why.

Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes.

Describe the role of glucagon in gluconeogenesis.

Do not include in your answer details on the second messenger model of glucagon action.

The gene that codes for glucagon is 9.531 kilobases in length. The DNA helix makes one complete turn every 10 base pairs. Every complete turn is 3.4 nm in length.

Use this information to calculate the length in micrometres (µm) of the gene for glucagon. Give your answer to 3 significant figures.

Metformin is a drug commonly used to treat type II diabetes. Metformin’s ability to lower the blood glucose concentration involves a number of mechanisms including:

• increasing a cell’s sensitivity to insulin

• inhibiting adenylate cyclase.

Explain how increasing a cell’s sensitivity to insulin will lower the blood glucose concentration.

Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration.

Broken bones are repaired by cells called osteoclasts and osteoblasts.

Osteoblasts secrete a hormone called osteocalcin in an inactive form. Osteocalcin is a protein. The active form of osteocalcin binds to a receptor on beta (β) cells in the pancreas, stimulating them to release insulin. Osteoblasts have receptors for insulin.

Figure 1 shows how the production of osteocalcin by osteoblasts is controlled by positive feedback.

The secretion of osteocalcin (in an inactive form) by osteoblasts is controlled by positive feedback.

Use information from Figure 1 to explain why this is positive feedback.

The acidic pH conditions created by osteoclasts cause the inactive form of the protein osteocalcin to change into the active form of osteocalcin.

Suggest how.

Binding of insulin leads to an increase in the rate of respiration in cells such as osteoblasts.

Explain how.

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Each year, a few people with type I diabetes are given a pancreas transplant. Pancreas transplants are not used to treat people with type II diabetes.

Give two reasons why pancreas transplants are not used for the treatment of type II diabetes.

The pancreas produces the hormone insulin.

Put a tick (✓) in the box next to the statement which describes incorrectly the action of insulin.

Scientists investigated the use of induced pluripotent stem cells (iPS cells) to treat type I diabetes in mice. The scientists used four transcription factors to reprogramme skin cells to form iPS cells. The scientists then stimulated the in vitro differentiation of iPS cells into pancreatic cells.

The scientists set up three experimental groups:

Group A – 30 mice with type I diabetes received pancreatic cell transplants derived from iPS cells.

Group B – 30 mice with type I diabetes were left untreated.

Group C – 30 mice without diabetes were left untreated.

The scientists measured the blood glucose concentration of all the mice on a weekly basis for 12 weeks.

The results the scientists obtained are shown in Figure 6.

Suggest how transcription factors can reprogramme cells to form iPS cells.

Using all the information provided, evaluate the use of iPS cells to treat type I diabetes in humans.