Control of Blood Glucose Concentration (AQA GCSE Biology): Revision Note
Exam code: 8461
Control of blood glucose
Blood glucose concentration is monitored and controlled by the pancreas
The pancreas is an endocrine gland that also plays a separate role in digestion
Blood glucose concentration must be kept within a narrow range, so glucose regulation is an example of homeostasis
A high level of glucose in the blood raises the solute concentration of the blood, causing water to leave surrounding cells by osmosis
A low level of glucose in the blood reduces availability of fuel for respiration
Eating foods containing carbohydrate results in an increase of glucose into the bloodstream; the following events then occur:
the pancreas produces the hormone insulin
insulin stimulates cells to take in glucose from the bloodstream (particularly liver and muscle cells)
in liver and muscle cells excess glucose is converted into glycogen for storage
Diabetes
Type 1 diabetes
Type 1 diabetes is a disorder in which the pancreas fails to produce sufficient insulin to control blood glucose levels
It occurs when the body’s immune system mistakenly attacks and destroys the insulin-producing cells in the pancreas
Type 1 diabetes is characterised by uncontrolled high blood glucose levels and is normally treated with insulin injections
Type 2 diabetes
In type 2 diabetes the body cells no longer respond to insulin produced by the pancreas—the person still makes insulin, but their cells are resistant to it and don’t respond as well as they should
This can also lead to uncontrolled high blood glucose levels
A carbohydrate-controlled diet and an exercise regime are common treatments for Type 2 diabetes
Type 2 diabetes is associated with risk factors such as:
obesity
a diet high in sugar and fat
a sedentary lifestyle
family history of Type 2 diabetes
age
Cause | Treatment | |
|---|---|---|
Type 1 diabetes | Inability of pancreas to produce insulin | Monitoring blood glucose levels and injecting human insulin throughout the day (particularly after meals consumed) |
Type 2 diabetes | Cells of the body become resistant to insulin | Maintain a carbohydrate-controlled diet and regular exercise to reduce need for insulin |
Interpreting information about blood glucose levels
Worked Example
Two individuals had their blood insulin and blood glucose levels measured after consuming a glucose drink. The results are shown in the table below.
Time after drink (mins) | Person A blood insulin (µU / mL) | Person A blood glucose (mmol / L) | Person B blood insulin (µU / mL) | Person B blood glucose (mmol / L) |
|---|---|---|---|---|
0 | 7 | 5.2 | 19 | 6.7 |
30 | 35 | 7.0 | 50 | 10.5 |
60 | 45 | 7.8 | 66 | 12.8 |
90 | 30 | 6.5 | 60 | 12.5 |
120 | 24 | 5.0 | 53 | 11.8 |
(a) State which of the two individuals is more likely to have untreated diabetes, and identify the type of diabetes they are likely to have.
(b) Give a reason for both parts of your answer to part (a).
Answer (a)
Individual B is more likely to have diabetes
They are likely to have type 2 diabetes
Answer (b)
Person B's blood glucose concentration is higher throughout OR B's glucose peaks at 12.8 compared with 7.8 OR person B's blood glucose is still high (11.8) at 120 minutes while A's returns to normal (5.0)
B is producing insulin, while a person with type 1 diabetes would produce little / no insulin OR B has higher blood insulin, indicating that their cells are not responding to insulin
Examiner Tips and Tricks
You should also be able to extract information and interpret data from graphs that show the effect of insulin on blood glucose levels in both people with diabetes and people without diabetes.
Negative feedback control of blood glucose
Higher Tier Only
Glucagon and insulin interact as part of a negative feedback cycle to control blood glucose (sugar) levels in the body:
Insulin is produced when blood glucose rises and stimulates liver and muscle cells to convert excess glucose into glycogen to be stored – this reduces the blood glucose level
Glucagon is produced when blood glucose falls too low and stimulates liver cells to convert stored glycogen into glucose to be released into the bloodstream – this increases the blood glucose level
Examiner Tips and Tricks
The terms glucagon and glycogen are very often mixed up by students as they sound similar; remember:
Glucagon is the hormone
Glycogen is the storage molecule for glucose in animal cells
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