Hormonal Communication (OCR A Level Biology)

Insulin is a hormone responsible for regulating blood glucose levels.

Explain how insulin affects body cells.

Diabetes is a condition in which the hormone insulin is unable to carry out its function. Metformin is a drug sometimes used to treat diabetes. 

A research group investigated the effect of metformin on blood glucose levels in 10 diabetic mice. The mice were given no food for 12 hours and were then given either no metformin (the control group), a 60 mg per kg dose of metformin, or a 400 mg per kg dose. 30 minutes later the mice were given a glucose meal and 180 minutes after this their blood glucose levels were measured. The results, along with bars to show standard deviation, are shown in Fig. 1.

Fig. 1

A research assistant concluded from these results that metformin was an effective drug for the treatment of diabetes in human patients.

Use Fig. 1 and the information provided to evaluate this conclusion.

The drug metformin works by lowering cellular levels of cyclic AMP.

Suggest how metformin works to reduce the impact of non-functioning insulin.

A simple indicator test for diabetes in a patient involves the use of a urine test strip.

State why urine test strips show the presence of glucose but not other sugars in the urine.

Explain why glucose is present in the urine of diabetic individuals.

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Fig. 1 shows a light micrograph of a pancreas.

Fig. 1

Identify the structures labelled A and B in Fig. 1.

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

Pancreas cells were first incubated with glucose at a concentration of 2.5 mmol dm⁻³. The concentration of glucose was then increased to 19.7 mmol dm⁻³ in the presence or absence of the drug.

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 ten times.

The results are shown in the table below. 

[2]

[2]

Name the type of cell that has most likely been affected by the new drug. 

The drug blocks Ca²⁺ channels.

Explain how blocking calcium channels could inhibit insulin secretion.

Figure 1 below shows the concentrations of glucose and insulin in the blood of an individual before and after a meal.

Fig. 1

After the meal, the concentrations of glucose and insulin in the blood increase.

Explain why there is a delay in the increase of insulin concentration following the increase in blood glucose concentration.

The shaded parts of the graph in Fig. 1 are over-simplified representations of the blood glucose and insulin concentrations.

Describe and explain how these concentrations may appear differently on a more accurately drawn graph.

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.

Insulin is secreted from the beta cells of the pancreas in response to increased blood glucose concentration.

Fig. 1 is a diagram representing the sequence of events leading to the secretion of insulin from the beta cell.

Fig. 1

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[2]

Another type of tissue that produces hormones is the adrenal gland. 

State and explain whether the adrenal glands are endocrine or exocrine glands?

Addison's disease, also called adrenal insufficiency, is a disease where the adrenal glands make too little cortisol and aldosterone.

People with Addison's disease often have to take artificial hormones in drugs to replicate the effects of the hormones they are lacking, such as cortisol. Cortisol levels in healthy people fluctuate throughout the day, and so the drugs must replicate this effect. 

Fig. 2 below shows a graph of normal cortisol levels in the human body throughout the day. 

Fig. 2

The increased cortisol levels in the morning, followed by a gradual decrease throughout the day, is known as the cortisol awakening response. 

The purpose of this response is not 100% known. Suggest why it might be beneficial to humans to have an increased cortisol level 30 minutes after awakening. 

Another condition linked to the cortisol awakening response occurs in some people with Type I diabetes. Dawn phenomenon is a condition where diabetic people have a spike in blood sugar in the morning and can become hyperglycaemic.

Suggest how Dawn phenomenon may be linked to the cortisol awakening response.