1. Hormones and the regulation of blood glucose
Aim:

2. Hormones Chemical messenger
Endocrine glands secrete the hormone into the blood
Has its effect at a different site (target site) to where it is made
Fits into receptor molecules on target cells and is therefore specific to the target
Small soluble organic molecules that travels in blood plasma
Effective in low concentrations and effects generally long lasting
Released by glands

3. Second messenger mechanism
Bind to receptors on the cell surface membrane creating a hormone-receptor complex
Second messenger released within the cell causing a series of enzyme controlled reactions
Required response is produced

4. Importance of blood glucose levels
Main respiratory substrate (only energy source for brain cells)
Lack of glucose causes fainting
Normal level per 100cm3 of blood is 90mg but can vary between mg

5. Sources of blood glucose
Diet – glucose released from breakdown of other carbohydrates eg starch, maltose, lactose and sucrose
Break down of glycogen – Broken down in the liver or muscles cells
Gluconeogenesis – Production of new glucose molecules from non-carbohydrates eg glycerol and amino acids

6. Involves 6 hormones
2 negative feedback systems
Rise – hyperglycaemia stimulates insulin secretion
Decrease –hypoglycaemia inhibits insulin secretion

7. Factors influencing blood glucose levels
When eating takes place and the types of food eaten
The amount of physical and mental activity
The presence of 3 hormones … insulin glucagon and adrenaline

8. Insulin Globular protein made up of 51 aa
Released by the islets of langerhans β cells in the pancreas in response to high blood sugar levels

9. Effects of insulin
Binds to the glycoprotein receptors found on almost all body cells, increasing absorbtion of glucose into cells (especially muscle cells) by the following mechanisms
The binding to receptors changes the structure of glucose transport protein channels (channels open)
An increase in number of carrier molecules in the membrane
Increases rate of respiratory processes lowering the cell glucose levels, therefore leading to a greater intake of glucose

10. Effects of insulin
Activates enzymes that convert glucose to glycogen (glycogenesis) in liver and muscle cells
Glucose glucose phosphate glycogen
Increases conversion of glucose to fat
Insulin

11. Glucagon
Released by islet of Langerhans α cells the pancreas in response to low blood glucose levels
Activates the enzyme phosphorylase
The phoshorylase enzyme catalyses the breakdown of glycogen in the liver (glycogenolysis)
Glycogen glucose phosphate glucose
phosphorylase

12. Glucagon
Stimulates the synthesis of glucose from glycerol and amino acids (gluconeogenesis)
Glycerol  glucose
Amino acids  glucose

13. Adrenalin
Adrenalin released by the adrenal medulla in times of danger, stress and cold.
Stimulates conversion of glycogen to glucose (glycogenolysis) by activating an enzyme
Stimulates the synthesis of glucose from glycerol and amino acids (gluconeogenesis)
Inactivates an enzyme that synthesises glycogen from glucose

14. The role of the liver
The liver is the site where the following processes occur
Glycogenesis - (glucose to glycogen)
Gluconeogenesis (amino acids/glycerol to glucose
Glycogenolysis (glycogen to glucose)

15. Role of the pancreas Produces insulin and glucagon
Islets of Langerhans β cells – Detect high glucose levels - produce insulin
Islets of Langerhans α cells – Detect low glucose levels - produce glucagon

16. The factors that influence blood glucose concentration.
The role of the liver in glycogenesis and gluconeogenesis.
The role of insulin and glucagon in controlling the uptake of glucose by cells and in
activating enzymes involved in the interconversion of glucose and glycogen. The
effect of adrenaline on glycogen breakdown and synthesis.
The second messenger model of adrenaline and glucagon action.
Types I and II diabetes and control by insulin and manipulation of the diet.

17. TASK
Research and presentation of findings on Type I and Type II diabetes and how they can be controlled by insulin and diet.