16.3 - Hormones and the regulation of blood glucose concentration

Question 1

What are the properties of hormones?

Answer 1

• Produced in glands , secrete hormones directly into the blood (endocrine glands)
• Carried in the blood plasma to the cells on which they act (target cells - specific receptor on their cell surface membrane that is complmentary to hormone)
• Effective in low concentration but have widespread and long-lasting effects

Question 2

What is the second messenger model?

Answer 2

Mechanism is used by two hormones involved in the regulation of blood glucose concentration (adrenaline and glucagon)

Question 3

Steps of the second messenger model:

Answer 3

1. Adrenanline binds to the transmembrane protein receptor within the cell-surface membrane of liver cell
2. Binding of adrenanline causes the protein to change shape of the inside of membrane
3. Change of protein shape leads to the activation of an enzyme called adenly cyclase
4. Activiated adenly cyclase converts ATP to cyclic AMP (cAMP)
5. cAMP acts as a second messenger that binds to the protein kinase enzyme , changing its shape and activating it
6. Active protein kinase enzyme cataylses the conversion of glycogen to glucose (glycogneolysis)which moves out of liver cell by faciliated diffusion and into the blood by channel proteins

Question 4

Diagram of second messenger model

Answer 4

Question 5

Appearence of pancreas

Answer 5

It is a large, pale-coloured gland that is situated in the upper abdomen behind the stomach

Question 6

What is the function of the pancreas?

Answer 6

It produces enzymes (protease, amylase and lipase) for digestion and hormones (insulin and glucagon) for regulating blood glucose concentration

Question 7

What is seen under the pancreas microscopically?

Answer 7

• Made up largely of cells that produce its digestive enzymes
• Scattered throughout the cells are groups of hormone-producing cells known as islets of Langerhans

Question 8

What are the cells of islets of Langerhans inclucde?

Answer 8

• Alpha cells which are larger and produce the hormone glucagon
• Beta cells which are smaller and produce the hormone insulin

Question 9

Where is the liver located in?

Answer 9

Below the diaphragm

Has a mass up to 1.5kg and made up of cells called hepatocytes

Question 10

What is the role of the liver?

Answer 10

• Serves a variety of roles
  
  • Regulating blood glucose concentration
• While the pancreas produce hormones of insulin and glucagon its the liver thar has the effects

Question 11

What are the three important processes regulating the blood sugar which takes place in the liver?

Answer 11

• Glycogenesis
• Glycogenolysis
• Gluneogenesis

Question 12

What is glycogensis?

Answer 12

It is the conversion of glucose into glycogen

Question 13

When does glycogenesis happens?

Answer 13

When the blood glucose concentration is higher than normal

Liver removes glucose from the blood and coverts to glycogen

It can store 75-100g of glycogen which is sufficient to maintain human blood glucose concentration for 12 hours in absence of other sources

Question 14

What is glycogenolysis?

Answer 14

It is the breakdown of glycogen to glucose

Question 15

When does glycogenolysis happen?

Answer 15

When the blood glucose concentration is lower than normal

Liver can convert stored glycogen back into glucose

This can diffuse into the blood to restore the normal blood glucose concentration

Question 16

What is gluconeogenesis?

Answer 16

It is the production of glucose from sources other than carbohydrate

Question 17

When does gluconeogenesis happen?

Answer 17

When its supply of glycogen is exhausted

The liver can produce glucose from non-carbohydrate sources such as glycerol and amino acids

Question 18

What is glucose a source for?

Answer 18

It is a substrate of respiration

providing the source of energy for almost all organisms

Therefore, it is essential that blood of mammals contains a relatively constant concentration of glucose for energy

Question 19

What happens if the blood glucose concentration falls below the normal?

Answer 19

Cells will be deprived of energy and die especially brain cells are sensitive to this as they only respire glucose

Question 20

What happens if the blood glucose concentration rises too high?

Answer 20

It lowers the water potential of blood and creates osmosis problems

causes dehydration and equally dangerous

Question 21

Wha factors influence the blood glucse concentration?

This is where blood glucose from from three sources

Answer 21

• Diet - in form of glucose absorbed following hydrolysis of other carbohydrates such as starch, maltose and sucrose
• Glycogneogensis (hydrolysis in small intestine of glycogen) stored in lvier and muscle cells
• Gluconeogenesis - which is the production of glucose from sources other than carbohydrates

Question 22

What is insulin?

Answer 22

A globular protein made up of 51 amino acids

A hormone

Question 23

What cells do not have glycoprotein receptors on cell surface membrane?

Answer 23

Red blood cells

Almost all body cells have this

Question 24

What happens when the insulin binds into the glycoproteins receptor on cell-surface membrane ?

Answer 24

• A change in tetiary structure of gluocse transport carrier proteins , causing them to change shape and open
• This allows glucose to move in cell by facilitaed diffusion
• Increase in carrier proteins responsible for transport of cell-surface membrane. At low insulin , protein which channels are part of membrane of vesicles
• A rise in insulin concentration result in these vesicles fusing increasing no of glucose transport chain
• Activation of enzymes to convert glucose to glcygoen and fat

Question 25

How is blood glucose concentration is lowered in one or more of the fllowing ways?

Answer 25

* Increasing rate of absorbption of glucose into muscle cells * Increasing respiration rate of cell using more glucose * Increasing the conversion of glucose into glycogen (glycogenesis) in the cells of liver and muscles * Increasing the rate of conversion of glucose to fat

Question 26

What is the glucagon's actions at secreting at blood plasma?

Answer 26

* Attaching specific protein receptor on cell-surface membrane of liver cells * Activating enzymes that convery glycogen to glucose * Activating enzymes involved in the conversion of amino acid and glycerol into glucose (=gluconeogensis)

Question 27

What is the effect of adrenanline in blood gluocse concentration?

Answer 27

Increase this

Question 28

When is adrenanline produced and produced by?

Answer 28

Produced by the adrenal glands This is produced by times of excitment and stress

Question 29

Where is the adrenal glands located at?

Answer 29

Above the kidney

Question 30

How does adrenaline gland increase the blood glucose concentration by?

Answer 30

* Attaching to protein receptors on cell surface membrane of target cells * Activating enzymes that causes the breakdown of glycogen to glucose in liver

Question 31

How does insulin and glucagon hormones act anatgonistically?

Answer 31

The system is self-regulating through negative feedback The concentration of glucose in blood determine the quantity of insulin and glucagon produced Only when falls - insulin produced Only when rises - glucagon produced

Question 32

Explain why the events shown in diagram can be described as an example of negative feedback?

Answer 32

Because it has changes to bring it back to normal level It changes from the normal Minimises effect

Question 33

Steps What happens if blood glucose concentration increases above the normal?

Answer 33

* B cells (islets of Langerhans) detect the change (receptors) * B cells release insulin (found in blood plasma) * This targets organs of liver and muscles * This increase the glucose uptake * Increase the glucose transport proteins in all cells * Increase glycogenesis * Increase rate of respiration * This decreases the blood glucose level

Question 34

Steps What happens if blood glucose concentration decreases above the normal?

Answer 34

1. Alpha cells in iselts of Langerhans detect the change 2. Alpha cells release glucagon in blood plasma 3. Target organs liver and muscles 4. This increase glycogenolysis (glycogen to glucose) 5. This decreases glcuose uptake 6. Decrease rate of respiration 7. IGluconeogenesis - glucose from amino acids + glycerol 8. Decrease glucose transport proteins

Question 35

What processes increase during second messeger model?

Answer 35

Glycogneolysis increases glycognegensis increases glycognesis decreases Adrenanline acts as a 1st messenger