Topic 6: Blood Glucose

Question 1

What hormones are involved in the control of blood glucose concentration?

Answer 1

Insulin
Glucagon
Adrenaline

Question 2

What is the average blood glucose concentration in a human?

Answer 2

90mg per 100cm3
There is a narrow range of 70-100mg

Question 3

Why is it important that the blood concentration is maintained ?

Answer 3

Cells need a constant/consistent supply of glucose for respiration
Glucose is a major respiratory substrate

Question 4

What is the source of glucose in the diet?

Answer 4

Carbohydrates

Question 5

Summarise what will happen if the blood glucose level falls too low

Answer 5

Cells will die
Brain cells for example, can only respire glucose and not use other organic molecules as respiratory substrates so they would die

Question 6

Summarise what would happen if the concentration of blood glucose what’s too high

Answer 6

It lowers the water potential of blood and creates osmotic problems that can cause dehydration

Question 7

What are the sources of blood glucose

Answer 7

Absorption from the gut after the digestion of carbohydrates
The breakdown of glycogen stored in liver and muscle cells
The conversion of non-carbohydrates into glucose

Question 8

What is the name given to the conversion of non-carbohydrates (e.g. lactate, fats and amino acids) into glucose?

Answer 8

Gluconeogenisis

Question 9

What is the role of the pancreas?

Answer 9

It is mainly involved in producing enzymes for digestion
It is involved in regulations blood glucose by producing insulin and glucagon

Question 10

How is the pancreas involved in regulating blood glucose?

Answer 10

1-2% of pancreatic tissue is made up of clusters of cells that produce hormones, known as the islets f langerhans

Question 11

What are the Islets of Langerhans?

Answer 11

They are clusters of cells in the pancreas
They have 2 cell types: alpha and beta
Alpha produce glucagon
Beta produce insulin

Question 12

What do alpha cells produce?

Answer 12

Glucagon

Question 13

what do beta cells produce?

Answer 13

Insulin

Question 14

What is the role of the liver?

Answer 14

The insulin and glucagon produced in the pancreas have effects in the liver
It is where glycogenesis, glycogenolysis and gluconeogenesis occur

Question 15

Glycogenesis

Answer 15

Conversion of glucose to glycogen

Question 16

Glycogenolysis

Answer 16

Breakdown of glycogen to glucose

Question 17

Gluconeogenesis

Answer 17

Production of glucose from other sources than glucose

Question 18

What happens when there is a rise in blood glucose?

Answer 18

1. Rise is detected by beta cells, they then produce insulin
2. Vesicles of insulin move to the membrane and release it into the capillaries
3. Insulin diffuses into the blood
4. Insulin attaches to receptor molecules on cell membranes- especially adipose storage tissue, muscles and liver

Question 19

What does insulin do ?

Answer 19

• causes a change in the tertiary structure of channel proteins in the liver and muscle cells so they open
• increase in number of channel proteins in the membranes of muscle and adipose cells
  -Activation of enzymes in the liver to convert glucose to glucose phosphate
  -activation of enzymes in the liver and muscles for glycogenesis
  -activation of enzymes in the adipose tissues to convert glucose to fat
• an increase in the rate of aerobic respiration in cells

Question 20

Insulin causes a change in the tertiary structure of channel proteins in the membranes of liver and muscle cells so they open. How does that lower the blood glucose concentration?

Answer 20

More glucose molecules enter the liver and muscle cells by facilitated diffusion

Question 21

Insulin results in an increase in the number of channel proteins (GLUT-4) in the membranes of muscle and adipose cells. How does this lower blood glucose?

Answer 21

The rate of uptake of glucose from the blood by facilitated diffusion is increased because of the increased permeability of the cell membrane

Question 22

Insulin results in enzymes being activates in the adipose tissue to convert glucose to fat. How does this lower the blood glucose concentration?

Answer 22

It maintains a steep diffusion gradient between the blood and cells, so the rate of uptake of glucose is increased

Question 23

Insulin causes an increase in the rate of aerobic respiration in cells. How does this lower blood glucose?

Answer 23

Cells respire more glucose, so they increase their uptake from the blood

Question 24

What does the action of insulin result in?

Answer 24

Blood glucose concentration returning to normal
Beta cells reduce their secretion of insulin
It’s an example of negative feedback

Question 25

When does the blood concentration fall?

Answer 25

During exercise or when a person is fasting or starving This is because glucose has been used for cellular respiration

Question 26

What happens when the blood glucose drop?

Answer 26

When it drops below 90mg per 100cm3, the secretion of insulin stops Alpha cells in the islets of Langerhans secrete glucagon Glucagon diffuses into the blood and mainly affects liver cells

Question 27

What does glucagon do?

Answer 27

Causes the activation of enzymes in the liver that: - breakdown stored glycogen into glucose(glycogenolysis) -convert other substances to glucose (gluconeogenesis)

Question 28

What happens as a result of glucagon acting?

Answer 28

Blood glucose increases Alpha cells reduce secretion of glucagon (example of negative feedback)

Question 29

What is the relationship between insulin and glucagon?

Answer 29

They act antagonistically (in opposite directions)

Question 30

Where and when is adrenaline produced?

Answer 30

By the adrenal glands In times of excitement,stress,exercise, when blood concentration is low

Question 31

Explain the role of adrenaline in the control of blood glucose concentration

Answer 31

-it binds to protein receptors on the cell surface membrane of liver cells -activates enzymes in the liver to cause glycogenolysis, and inhibit enzymes that carry out glycogenesis - activates secretion of glucagon but inhibits insulin

Question 32

What happens as a result of adrenaline in the control of blood glucose?

Answer 32

More glucose is available for respiring muscles It allows a boost of respiratiory substrate for more respiration and more muscle contraction for fight or flight

Question 33

What is the second messenger model?

Answer 33

The mechanism used by adrenaline and glucagon which both activate glycogenolysis inside cells

Question 34

Summarise what the second messenger model does

Answer 34

It works where hormones bind to cell receptors which activate enzymes on the inside of cell membranes, which then produces a chemical known as a second messenger The second messenger activates other enzymes to in the cell to bring a response

Question 35

What is the first messenger ?

Answer 35

Adrenaline

Question 36

Adrenaline is the first messenger, what does it do?

Answer 36

It and glucagon bind to the specific receptors on the cell surface membrane of target cells to form a hormone receptor complex The hormones receptor complex activates an enzyme inside the cell

Question 37

What enzyme is activated by the hormone-receptor complex in the second messenger model?

Answer 37

Adenylate cyclase

Question 38

What does adenylate cyclase do in the second messenger model?

Answer 38

It converts ATP into cAMP by removing 2 phosphate groups CAMP acts as a second messenger

Question 39

What is the second messenger?

Answer 39

cAMP

Question 40

What does cAMP do in the second messenger model?

Answer 40

It activates protein kinase which activates a set of chain reactions to bring about the breakdown of glycogen to glucose

Question 41

Why is ADP more common than AMP, when more energy would be released from the hydrolysis of AMP?

Answer 41

It isnt as energy efficient to resynthesise 2 phosphates

Question 42

How many types of diabetes are there?

Answer 42

2

Question 43

Which type of diabetes is insulin dependent?

Answer 43

Type 1

Question 44

What type of diabetes is insulin independent?

Answer 44

Type 2

Question 45

Causes of type 1 diabetes

Answer 45

It is an auto immune condition The body’s T cells attack and destroy beta cells so there is a shortage of insulin Pancreas cannot produce insulin It begins in childhood

Question 46

What is the effect of type 1 diabetes?

Answer 46

It can lea to high levels of blood glucose concentration after a meal and it can affect the brain, leading to coma or death

Question 47

What are the symptoms of type 1 diabetes?

Answer 47

Glucose appears in urine (kidney cannot absorb it all) Urinating frequently Thirst Tiredness Weight loss

Question 48

Why does someone with type 1 diabetes urinate frequently and feel thirsty?

Answer 48

More glucose in urine means less water is reabsorbed

Question 49

How is type 1 diabetes treated?

Answer 49

Insulin injections- fast acting and slow acting insulin is available Management of exercise and carbohydrate intake

Question 50

Why does insulin have to be injected in the treatment of type 1 diabetes?

Answer 50

It is a protein If it was ingested it would be digested

Question 51

What is the hazard of treatment for type 1?

Answer 51

If a diabetic takes too much insulin, it could lower blood glucose too much which results in unconsciousness

Question 52

What is the cause of type 2 diabetes?

Answer 52

Glycoprotein receptors in the body, especially in liver and fat storage tissue lose their responsiveness to insulin May also be due to inadequate supply of insulin from the pancreas

Question 53

What is type 2 diabetes related to and how is this seen?

Answer 53

Often related to obesity Tends to occur in over 40s, but more and more common in obese adolescents 90% of UK diabetes cases are type 2

Question 54

What are the symptoms of type 2 diabetes?

Answer 54

Symptoms develop slowly and may be unnoticed Possible symptoms: tiredness, blurred vision, sugar in urine

Question 55

How is type 2 diabetes treated?

Answer 55

Regulation of carbohydrate intake Lower fat content of diet Exercise is needed Drugs may be needed to stimulate insulin production May need insulin injections