Control of blood glucose concentration Flashcards
What do cells need to work?
Constant energy supply
What is the normal concentration of blood glucose?
90mg per 100cm3 of blood
What monitors blood glucose concentration?
Pancreas
What makes blood glucose concentration rise?
After eating foods containing carbohydrates
What makes blood glucose concentration fall?
After exercise
What 2 hormones control blood glucose concentrations?
Insulin
Glucagon
Where to hormones travel to?
Travel in blood to their target cells (effectors)
Where are insulin and glucagon secreted?
Islets of Langerhans in the pancreas
What do insulin and glucagon do?
Act on effectors which respond to restore the blood glucose concentrations to normal levels
What cells secrete insulin?
Beta cells
What cells secrete glucagon?
Alpha cells
What does insulin do?
Lowers blood glucose concentration when it is too high
How does insulin work?
- Insulin binds to specific receptors on the cell membranes of liver and muscle cells.
- It increases the permeability of muscle cell membranes to glucose so the cells take up more glucose. It involves increasing the number of channel proteins in membrane.
- Insulin activates enzymes in liver/muscle cells that convert glucose into glycogen.
- Cell are able to store glycogen in their cytoplasm as an energy store.
- The process of forming glycogen from glucose is called glycogenesis.
- Insulin also increases the rate of respiration of glucose
What does glucagon do?
It raises blood glucose concentration when it’s too low
How does glucagon work?
- Glucagon binds to specific receptors on the cell membranes of liver cells.
- Glucagon activates enzymes in liver cells that break down glycogen into glucose.
- The process of breaking down glycogen is called glycogenolysis.
- Glucagon also activates enzymes that are involved in the formation of glucose from glycerol and amino acids.
- The process of forming glucose from non-carbohydrates is called gluconeogenesis.
- Glucagon decreases the rate of respiration of glucose in cells
What process is activated by insulin?
Glycogenesis
What processes is activated by glucagon?
Glycogenolysis
Gluconeogenesis
What happens when there is a rise in blood glucose concentration?
Detected by pancreas.
Beta cells secrete insulin
Alpha cells stop secreting glucagon
Insulin binds to receptors on liver and muscle cells
- Cells take up more glucose
- Glycogenesis is activated
- Cells respire more glucose
Less glucose in the blood returns the blood glucose concentration to normal
What happens when there is a fall in blood glucose concentration?
Detected by pancreas
Alpha cells secrete glucagon
Beta cells stop secreting insulin
Glucagon binds to receptors on liver cells
- Glycogenolysis is activated
- Gluconeogenesis is activated
- Cells respire less glucose
Cells release glucose into the blood to return the blood glucose concentration back to normal
What is GLUT4?
A glucose transporter (channel protein) that is found in skeletal and cardiac muscles
What does GLUT4 do?
When insulin levels are low GLUT4 is stored in vesicles in the cytoplasm of cells. When insulin bonds to receptors on the cell surface membrane it triggers the movement of GLUT4 to the membrane. Glucose can then be transported into the cell through GLUT4 by facilitated diffusion.
What is adrenaline?
A hormone that is secreted from your adrenal glands
When is adrenaline secreted?
When there is a low concentration of glucose in your blood, when you are stressed and when you are exercising
Where does adrenaline bind to?
Receptors in the cell membranes of liver cells
