Regulation of blood glucose concentration Flashcards
Protein hormones
- Binds to receptor on the plasma membrane
= Conformational change - Initiating production of enzyme adenylyl cyclase
= Cells converts ATP into cyclic adenosine monophosphate (cAMP) - Activates enzymes to carry out normal function
The pancreas
- Mainly made up of cells that produce digestive enzymes; amylase, lipase and protease.
- Hormone producing cells called islets of Langerhans - involved in the regulation of blood glucose levels
Islets of Langerhans
- Glucagon hormone produced by a cells - larger
- Insulin hormone produced by B cells - smaller
Three important processes
1 - Glycogenesis
2 - Glycogenolysis
3 - Gluconeogenesis
Glycogenesis
- Conversion of glucose into glycogen
- Happens when blood glucose levels are higher than normal
- Liver removes glucose from the blood
- Converts it into glycogen for storage
Glycogenolysis
- Breakdown of glycogen to glucose
- Happens in the liver when blood glucose levels are lower than normal
Gluconeogenesis
- Production of glucose from sources other than carbohydrates;
Amino acids
Glycerol
Why is it important for organisms to maintain the correct level of glucose in the blood
- Maintain water potential of cells and metabolism
- So cells don’t shrivel or burst
Normal blood glucose concentration
5 mmol dm-3
3 sources of glucose for the blood
- Diet - direct glucose or hydrolysed carbohydrate
- Glycogenolysis - hydrolysis of glycogen
- Gluconeogenesis - production of glucose from sources other than carbohydrates
Fluctuation
- Depending on diet and activity levels (respiration rates)
- Positive and negative feedback
Beta cells of islets of Langerhans
- Receptors that detect high blood glucose levels
- Secrete insulin directly into the blood
- Transported in blood plasma until it reaches a cell with complementary receptors on its surface
= Insulin receptor complex
The effect of insulin
- Glucose transport carrier proteins change shape and open allowing more glucose to move through them by F.D into the cell
- Enzymes involved in conversion of glucose to glycogen and fat are activated
- More glucose transport channels are created
Negative feedback - insulin
- Stop the secretion of insulin once the blood glucose level returns to normal
Importance of an increased glucose uptake
- Water potential of the blood is maintained
Importance of an increased respiratory rate
- Use the glucose in respiration which will lower the glucose levels and provide you with more energy (ATP)
Importance of an increased glycogenesis
- Reduces blood sugar levels
- Acts as a store for glycogen for later activity
Importance of an increased lipogenesis
- Creation of fats
- Store of glucose when blood sugar levels are low
The role of glucagon
- Alpha cells of the islets of Langerhans have receptors that detect low blood glucose levels
- Secrete glucagon directly into the blood which is transported in the blood plasma until it reaches a cell with complementary receptors on its surface
- Glucagon receptor complex is formed
The effect of glucagon
- Activates enzymes that convert glycogen to glucose
- Activates enzymes that convert amino acids and glycerol into glucose GLUCONEOGENESIS
Negative feedback - effect of glucagon
- Stop the secretion of glucagon once the blood glucose level returns to normal
Adrenaline
- Regulates blood glucose levels - stress and excitement
- Adrenaline secreted from adrenal gland
- Adrenaline attaches to complementary protein receptors on the cell surface membrane of target cells
- Activates enzymes - breakdown of glycogen to glucose in the liver
- Respiration rate increases
Blood glucose level rises
- Beta cells in pancreas releases insulin into the blood
- Liver takes up glucose and stores it as glycogen
- Blood cells take up glucose
- Blood glucose levels decline
- Homeostasis
Blood glucose levels falls
- Alpha cells in pancreas release glucagon
- Liver breaks down glycogen and releases glucose
- Blood glucose level rise
- Homeostasis
