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AS/A-Level Biology > I/E: Control of Blood Glucose Concentration > Flashcards

I/E: Control of Blood Glucose Concentration Flashcards

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1
Q

What is blood glucose monitored by?

A

Cells in the pancreas.

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2
Q

What is the normal concentration of glucose in the blood?

A

Around 90mg per 100cm3

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3
Q

What happens to blood glucose after exercise?

A

It falls - as more glucose is used in respiration to release energy.

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4
Q

What happens to blood glucose concentration after eating carbohydrates?

A

It rises

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5
Q

What two hormones control blood glucose concentration?

A

Insulin and glucagon

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6
Q

What secretes insulin into the blood?

What secretes glucagon into the blood?

A

Insulin = beta cells in the islets of Langerhans

Glucagon = alpha cells in the islets of Langerhans

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7
Q

What is the role of insulin in controlling blood glucose?

A

It lowers blood glucose concentration when it is too high.

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8
Q

How does insulin lower blood glucose concentration?

A
  1. Insulin binds to receptors on cell membranes of liver cells and muscle cells.
  2. Increases the permeability of muscle-cell membranes to glucose.
  3. Cells take up glucose by increasing the number of channel proteins in the cell membranes.
  4. Insulin also activates enzymes in liver and muscle cells that convert glucose to glycogen - glycogenesis.
  5. Insulin also increases the rate of respiration of glucose, esp. in muscle cells.
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9
Q

What is the role of glucagon in controlling blood glucose concentration?

A

It raises blood glucose concentration when it’s too low.

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10
Q

How does glucagon raise blood glucose concentration?

A
  1. Glucagon binds to receptors on cell membranes of liver cells.
  2. Activates enzymes that break down glycogen into glucose - glycogenolysis.
  3. Glucagon also activates enzymes involverd in the formation of glucose from glycerol and amino acids -gluconeogenesis.
  4. Also decreases rate of respiration of glucose in cells.
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11
Q

Glycogenesis

A

The process of forming glycogen from glucose.

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12
Q

Glycogenolysis

A

The process of breaking down glycogen.

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13
Q

Gluconeogenesis

A

The process of forming glucose from non-carbohydrates.

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14
Q

What type of feedback mechanisms keep blood glucose normal?

A

Negative feedback

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15
Q

Describe the negative feedback mechanism when blood glucose is too high:

A
  • Pancreas detects change in blood glucose.
  • B cells secrete insulin, a cells stop secreting glucagon.
  • Insulin binds to receptors on liver and muscle cells.
    • Cells take up more glucose.
    • Glycogenesis is activated.
    • Cells respire more glucose.
  • Less glucose in the blood - normal concentration.
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16
Q

Describe the negative feedback mechanisms when blood glucose concentration is too low:

A
  • Pancreas detects change.
  • a cells secrete glucagon, B cells stop secreting insulin.
  • Glucagon binds to receptors on liver cells.
    • Glycogenolysis is activated.
    • Gluconeogenesis is activated.
    • Cells respire less glucose.
  • Cells release glucose into the blood - normal levels return.
17
Q

GLUT4

A

A channel protein that transports glucose in skeletal and cardiac muscle cells.

18
Q

Where is GLUT4 stored when insulin levels are low?

A

In vesicles in the cytoplasm of cells.

19
Q

What happens to GLUT4 when insulin binds to receptors on the cell-surface membrane?

A

It’s movement is triggered to the membrane.

GLUT4 can then be transported into the cell through the GLUT4 protein, by facilitated diffusion.

20
Q

When is adrenaline secreted?

A

When blood glucose concentration is low, when you’re stressed and when you’re exercising.

21
Q

What is the role of adrenaline in controlling blood glucose concentration?

A

Binds to receptors in the cell membrane of liver cells.

  • Activates glycogenolysis.
  • Inhibits glycogenesis.
  • Activates glucagon secretion and inhibits insulin secretion = increasing blood glucose.
22
Q

How does adrenaline get the body ready for action?

A

Makes more glucose available for muscles to respire.

23
Q

What is special about adrenaline and glucagon?

A

Act via a second messenger - can activate glycogenolysis inside a cell even though they bind to receptors outside the cell.

24
Q

Describe the second messenger model:

A
  1. Glucagon/insulin binds to receptors and activates adenylate cyclase.
  2. Converts ATP into a chemical signal called a ‘second messenger’ = cyclic AMP.
  3. cAMP activates enzyme protein kinase A.
  4. Protein kinase A activates a cascade that breaks down glycogen into glucose - glycogenolysis.
25
Q

Name a condition that occurs when blood glucose concentration is not controlled:

A

Diabetes mellitus

26
Q

What is the cause of Type 1 diabetes?

A

Immune system attacks B cells in islets of Langerhans so they don’t produce insulin.

Believed that a genetic predisposition or development of a viral infection might trigger this.

27
Q

In Type 1 diabetes, what happens after eating?

A

Blood glucose levels rise and stay high - hyperglycaemia.

Kidneys can’t reabsorb all the glucose and so some is excreted in urine.

28
Q

How is Type 1 diabetes treated?

A
  • Insulin therapy - regular insulin injections/insulin pump.
  • Eating regularly and controlling simple carbonhydrate intake to avoid sudden rise in glucose.
29
Q

What are the risk factors for Type 2 diabetes?

A
  • Obesity
  • Family history
  • Lack of exercise
  • Age
  • Poor diet.
30
Q

What is wrong with B cells in Type 2 diabetes?

A

B cells don’t produce enough insulin or when the body cells don’t respond properly to insulin because the insulin receptors on their membranes don’t work.

31
Q

How is Type 2 diabetes treated?

A
  • Eating a balanaced diet.
  • Weight loss.
  • Regular exercise.
  • Glucose-lowering medication can be taken.
  • Insulin injections may be needed.
32
Q

How have health advisors responded to the increase in Type 2 diabetes?

A
  • NHS campaigns like ‘Change4Life’ - educate people on healthier lifestyle choices.
  • Challenged food industry to reduce the advertising of junk food especially to children, to improve the nutritional value of products and to use clearer labelling on products.
33
Q

How have food companies responded to criticism?

A
  • Using sugar alternatives to sweeten food/drinks.
  • Reducing sugar, fat and salt content of products.
34
Q

What is the normal concentration of glucose in urine ?

A

Between 0 and 0.8 mM

35
Q

How is quantitative Benedict’s reagent different to normal Benedic’t reagent?

A

When heated with glucose, the initial blue colour is lost but a brick-red precipitate is not produced.

36
Q

What is a colorimeter used for?

A

To measure the light absorbance of the solution after the quantitative Benedict’s test has been carried out.

37
Q

Describe the absorbance of a solution with a high concentration of glucose:

A

The higher the concentration of glucose, the more blue colour will be lost, decreasing the absorbance of the solution.

38
Q

Describe how you would make a calibration curve and use it to test a urine sample:

A
  1. Perform a quantitative Benedict’s test on each solution and a negative control of pure water.
  2. (Add to a water bath that’s at boiling point)
  3. Use a colorimeter (with a red filter) to measure the absorbance of the Benedict’s solution remaining in each tube.
  4. Use results to make the calibration curve showing absorbance against glucose concentration.
  5. Test the urine sample, in the same way as the known concentrations, and use the claibration curve to find the concentration of glucose in the sample.

AS/A-Level Biology (190 decks)

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