6.4.2 Control of Blood Glucose Concentration

Question 1

Define endocrine system

Answer 1

Series of glands throughout body which produce and secrete hormones

Question 2

Define hormone

Answer 2

Chemical messengers transported around body in blood plasma to act on target cells

Question 3

What feature of target cells allows hormones to act on them?

Answer 3

Glycoprotein receptors on membrane complementary to specific hormone

Question 4

How does the endocrine system compare to the nervous system?

Answer 4

Slower but longer-lasting effects

Question 5

Give nine examples of glands that are part of the endocrine system

Answer 5

Pituitary gland
Thyroid
Thymus
Adrenal
Pancreas
Kidneys
Uterus
Ovaries 
Testes

Question 6

Give three factors that influence blood glucose levels

Answer 6

Diet
Breakdown of glycogen
Production of glucose from non-carbohydrate sources

Question 7

What is the normal blood glucose concentration?

Answer 7

5 mmol/dm3

Question 8

Why is blood glucose concentration regulation important?

Answer 8

Too high, water potential of blood falls

Too low, cells can’t respire and die

Question 9

Define glycogenesis

Answer 9

Glucose removed from blood and stored in cytoplasm of hepatocytes (liver cells) as glycogen by the liver

Question 10

Define glycogenolysis

Answer 10

Liver converts glycogen back into glucose and glucose diffuses into blood

Question 11

Define gluconeogenesis

Answer 11

Formation of glucose from non-carbohydrates by liver when glycogen supply is exhausted

Question 12

Describe the exocrine function of the pancreas

Answer 12

Secretes digestive enzymes into pancreatic duct by:
Pancreatic cells surround small tubules which drain into pancreatic duct
Pancreatic cells produce pancreatic juice made up of amylase, trypsinogen and lipase

Question 13

Describe the endocrine function of the pancreas

Answer 13

Secretes hormones from alpha/beta cells in islets of Langerhans directly into blood

Question 14

What kind of feedback controls blood glucose concentration?

Answer 14

Negative

Question 15

What happens when blood glucose is too high?

Answer 15

Insulin secreted by beta cells in islets of Langerhans

Insulin binds to specific receptors on surface membrane of cells

Question 16

How does the action of insulin binding to the receptors increase the intake of glucose from the blood into cells? How does this decrease blood glucose concentration?

Answer 16

Tertiary structure of glucose transport carrier proteins changes so they open
Number of glucose transport carrier proteins e.g. GLUT4 increase
Respiratory rate of cells increases so more glucose is used up so more glucose diffuses into cells

Question 17

How else does the action of insulin binding to the receptors decrease blood glucose concentration?

Answer 17

Activates enzymes for glycogenesis in liver/muscle cells and conversion of glucose into fat so the rate of these reactions increases

Question 18

Describe the action of glucagon to increase blood glucose concentration

Answer 18

Secreted by alpha cells in islets of Langerhan
Attach to specific protein receptors on cell-surface membrane of liver cells
Activates enzymes that perform glycogenolysis
Activating enzymes involved in the conversion of amino acids and glycerol into glucose (gluconeogenesis)
Decrease in rate of respiration

Question 19

Describe the action of adrenaline to increase blood glucose concentration

Answer 19

Attach to specific receptors on hepatocytes
Activates enzymes involved in glycogenolysis
Glucose secretion
Glycogensis inhibition
Inhibition of insulin secretion

Question 20

What does the second messenger model describe?

Answer 20

How glycogen and adrenaline are able to activate glycogenolysis inside a cell without entering it

Question 21

Besides glucagon and adrenaline, what four named molecules are involved in the second messenger model?

Answer 21

Adenylate cyclase
ATP
Cyclic AMP
Protein kinase

Question 22

Describe the process shown in the second messenger model (6 steps)

Answer 22

1. Glucagon or adrenaline bind to specific membrane receptor (first messenger)
2. Binding causes receptor to change shape on inside of membrane, activates adenylate cyclase
3. Activated adenylate cyclase converts ATP into cyclic AMP (cAMP)
4. cAMP (second messenger) activates protein kinase, causing protein kinase to change shape
5. Activated protein kinase catalyses glycogen into glucose
6. Glucose moves out of liver by facilitated diffusion through channel proteins into the blood

Question 23

Define diabetes

Answer 23

Metabolic disorder where blood glucose concentration can’t be controlled properly

Question 24

Give five symptoms of diabetes

Answer 24

Thirsty 
Tired
Blurred vision 
Weight loss
Cuts not healing

Question 25

What is the cause of type 1 diabetes?

Answer 25

Immune system attacks beta cells in islets of Langerhans so can’t produce insulin

Question 26

What are the causes of type 2 diabetes?

Answer 26

Glycoprotein receptors on cells don’t respond to insulin/beta cells don’t produce enough insulin

Question 27

How does the age of onset compare for type 1 and type 2 diabetes?

Answer 27

Type 1 develops quickly and tends to develop in childhood

Type 2 develops slowly, usually in adults over 40 but cases in young people increasing

Question 28

Give two treatments for type 1 diabetes

Answer 28

Monitor blood glucose concentration

Injecting insulin

Question 29

Give four treatments for type 2 diabetes

Answer 29

Healthy balanced diet
Regular exercise
Drugs to stimulate insulin production/reduced rate of absorption in small intestine,
Insulin injections