3.4.7 Hormones and the Control of Blood Glucose Concentration

Question 1

What organ monitors blood glucose concentration?

Answer 1

Pancreas

Question 2

When blood glucose levels are too low, why is the brain most vulnerable?

Answer 2

∵ only respire glucose

Question 3

Name 4 factors that affect glucose concentration

Answer 3

• Rate of activity
• Diet
  
  • Starch is hydrolysed
  • Hydrolysis of lactose and sucrose
• Hydrolysis of glycogen
• Making glucose from non-carbohydrates sources, amino acids + glycerol

Question 4

Where is insulin and glucagon secreted from?

Answer 4

islets of Langerhans

(clusters of cells in pancreas)

Question 5

Which cells secrete insulin into the blood?

Answer 5

β cells

Question 6

Which cells secrete glucagon into the blood?

Answer 6

α cells

Question 7

Describe how insulin lowers blood glucose conc. when it’s too high

Answer 7

1. Insulin binds to specific receptors on cell membranes of liver & muscle cells
   
   • Increases permeability of muscle-cell membranes to glucose
     
     • Allows cells to take up more glucose
2. Insulin activates enzymes in liver and muscle cells that convert glucose to glycogen (glycogenesis)
   
   • Cells able to store glycogen in their cytoplasm as an energy source
3. Insulin increases rate of respiration of glucose (especially in muscle cells)

Question 8

How does insulin increase the permeability of muscle-cell membranes to glucose?

Answer 8

Changes the tertiary structure of glucose transport protein channels

Question 9

What is GLUT4?

Answer 9

Glucose transporter

(channel protein)

Question 10

Where is GLUT4 found?

Answer 10

Skeletal and cardiac muscle cells

Question 11

Describe what happens to GLUT4 when insulin levels are low

Answer 11

GLUT4 is stored in vesicles in the cytoplasm of cells

Question 12

What happens to GLUT4 when insulin levels are high and what does this allow?

Answer 12

• When insulin binds to receptors on cell-surface membrane, it triggers the movement of GLUT4 to membrane
• Glucose can be transported into cell through GLUT4 protein by facilitated diffusion

Question 13

Describe how glucagon raises blood glucose concentration when it’s too low

Answer 13

1. Glucagon binds to specific receptors on cell membranes of liver cells
2. Glucagon actives enzymes in liver cells that break down glycogen into glucose (glycogenolysis)
3. Glucagon activates enzymes that form glucose from glycerol and amino acids
   
   • Known as gluconeogenesis
4. Glucagon decreases rate of respiration of glucose in cells

Question 14

Where is adrenaline secreted from?

Answer 14

Adrenal glands

Question 15

When is adrenaline secreted?

Answer 15

When there’s low conc. of glucose in your blood, when you’re stressed and when you’re exercising

Question 16

Describe how adrenaline increases blood glucose concentration

Answer 16

1. Adrenaline binds to receptors in cell membrane of liver cells
2. Activates glycogenolysis
3. Inhibits glycogenesis
4. Activates glucagon secretion and inhibits insulin secretion

Question 17

How does adrenaline get the body ready for action?

Answer 17

Makes more glucose available for muscles to respire

Question 18

What can adrenaline and glucagon both do & how?

Answer 18

• Both can activate glycogenolysis inside cell even though they bind to receptors on outside of the cell
• Act via a second messenger

Question 19

Describe how adrenaline and glucagon act via a second messenger

Answer 19

1. Adrenaline and glucagon bind to receptors and activate enzyme = adenylate cyclase (aka adenylyl cyclase)
2. Adenylate cyclase converts ATP into cAMP (second messenger)
3. cAMP activates protein kinase A (enzyme)
4. Protein kinase A activates a cascade (chain of reactions)
   
   • = catalyses glycogenolysis

Question 20

Describe what occurs in type 1 diabetes

Answer 20

Immune system attacks β cells ≠ produce insulin

Question 21

How is type 1 diabetes caused?

Answer 21

• disease triggered by viral infection
• Some people have genetic predisposition for it

Question 22

What is it called when blood glucose is very high?

Answer 22

Hyperglycaemia

Question 23

What is it called when blood glucose is very low?

Answer 23

Hypoglycaemia

Question 24

For diabetic people, why is glucose found in their urine?

Answer 24

Kidneys can’t reabsorb all glucose ∴ some excreted in urine

Question 25

How is type 1 diabetes treated?

Answer 25

Treated with insulin therapy

• Take regular insulin injections throughout day
• OR some use insulin pump to deliver insulin continuously

Question 26

Why does insulin levels have to be carefully controlled?

Answer 26

∵ too much insulin = very low blood glucose levels = hypoglycaemia

Question 27

What can people with type 1 diabetes also do as well insulin therapy?

Answer 27

Eat regularly and control simple carbohydrate intake

Question 28

Name 4 risk factors for type 2 diabetes

Answer 28

• Obesity
• Lack of exercise
• Age
• Poor diet

Question 29

When does type 2 diabetes occur?

Answer 29

When β cells don’t produce enough insulin or when body’s cells don’t respond to insulin

Question 30

Why does body’s cells not respond to insulin in type 2 diabetes & what does this mean?

Answer 30

• ∵ receptors on membranes don’t work properly
  
  • tertiary structure has changed
• ∴ cells don’t take up enough glucose
  
  • Means blood glucose conc. is higher than normal

Question 31

How can type 2 diabetes be treated?

Answer 31

• By eating a healthy, balanced diet, losing weight and regular exercise
• Glucose-lowering medication
• Insulin injections

Question 32

Explain why this symptom of diabetes occurs: increased hunger and thirst

Answer 32

• Glucose from blood can’t enter cells ∴ body can’t convert food you eat into energy
  
  • Lack of energy = increase in hunger
• Thirsty ∵ urinate a lot

Question 33

Explain why this symptom of diabetes occurs: need to urinate excessively

Answer 33

When there’s excess glucose present in blood → kidneys react by flushing it out of blood and into urine

Question 34

Explain why this symptom of diabetes occurs: tiredness

Answer 34

• Due to high blood glucose levels
  
  • Causes slower circulation
• Due to low blood glucose levels

Question 35

Explain why this symptom of diabetes occurs: weight loss

Answer 35

• Glucose from blood can’t get into body’s cells to use as energy
• ∴ body starts burning fat and muscle for energy = reduction in overall body weight

Question 36

Explain why this symptom of diabetes occurs: blurred vision

Answer 36

High blood glucose levels = lens of eye to swell

Question 37

Explain why this symptom of diabetes occurs: genital itching, recurring thrush infection

Answer 37

High conc. of glucose → provides conditions for yeast infections

Question 38

State what you could use to determine the concentration of glucose in a urine sample

Answer 38

Colorimetry

Question 39

Explain why many people who suffer from Type 2 diabetes often have high blood pressure (3)

Answer 39

• High glucose in blood
• Lowers water potential of blood
• Diffusion/osmosis of water from cells into the blood
• Increases blood volume