Regulation Of Blood Glucose Concentration Flashcards
What conversion regulates blood glucose concentration
Liver converts between glycogen and glucose
3 processes within the liver when insulin and glucagon bind to membranes of liver cells
Glycogenesis
Glycogenolysis
Gluconeogenesis
What is glycogenesis
Synthesis of glucose -> glycogen
How is glycogenesis triggered
Insulin detects increased blood glucose concentration
Which processes are for increased/ decreased blood glucose concentration
Increased = glycogenesis glucose -> glycogen
Decreased = glycogenolysis glycogen -> glucose
How does glycogenesis work
Synthesises glycogen by removing glucose molecules form bloodstream which decreases blood glucose concentration
What is glycogen
Compact and efficient carbohydrate storage molecule
What is glycogenolysis
Glycogen -> glucose
How does glycogenolysis work
Glucagon triggers reaction
1) Glucagon detects decreased blood glucose concentration
2) Activates enzymes within the liver to breakdown glycogen molecules into glucose
3) Glycogen releases more glucose molecules to bloodstream which increases the blood glucose concentration back to normal
What does gluconeogenesis mean
Gluconeogenesis is synthesising non-carbohydrate molecules -> glucose
How does gluconeogenesis work
1) Glucagon triggers enzymes in liver to convert molecules into glucose (e.g. fatty acids, amino acids -> glucose)
2) Glucose molecules released into bloodstream which increases the blood glucose concentration to normal
3 ways glucose can enter the bloodstream
Absorption = digestion in gut
Hydrolysis = of glycogen
Non-carbohydrates converted to glucose
What hormones control glucose concenration
Insulin and glucagon
What organ regulates blood glucose
Pancreas
What does the pancreas produce to maintain blood glucose concentration
Enzymes - protease, amylase, lipase - for digestion
Hormones - insulin and glucagon - regulating bgc
How is blood glucose concentration regulated using hormones in the pancreas
1) Adrenaline (hormone) approaches transmembrane protein
2) Adrenaline fuses to receptor changing shape of the transmembranes active site forming an adrenaline-receptor complex - this stimulates adenyl cyclase (an enzyme) to be activated in the membrane
3) The activated adenyl cyclase converts ATP to cyclic AMP which acts as a second messenger
4) The cAMP changes the shape of activates protein kinase enzyme
5) The active protein kinase enzyme catalyses the conversion of glycogen to glucose
What is the pancreas made up of
Islets of Langerhans which are made up of alpha cells and beta cells
What do alpha and beta cells produce
Alpha cells = glucagon
Beta cells = insulin
What happens when blood glucose concentration rises too much or too low and how
Glucose provides energy to need to maintain concentration
Too low = cells deprives of energy and die, brain cells especially sensitive as they can only respire glucose
Too high = lowers water potential of blood creating osmotic problems, dehydrate
Blood glucose sources
1) Diet = absorbed form carbohydrates (starch, maltose, lactose, sucrose
2) Hydrolysis in small intestine of glycogen (glycogenolysis)
3) gluconeogenesis = production of glucose from other molecules
How is glucose concentration detected in pancreas
Beta cells of islets of Langerhans have receptors to detect when bgc too high
Secrete hormone insulin directly into blood plasma
What occurs when insulin binds to receptors on cell surface membranes of glycoproteins
1) Changes tertiary structure of glucose transporter carrier proteins = allowing more glucose into cells by facilitated diffusion
2) increase number of carrier proteins that transport glucose in cell surface membrane
3) activates enzymes to convert glucose -> glycogen and fat
Blood glucose concentration lowered how
Increase rate of:
1) absorption of glucose in cells
2) respiratory rate of cells (use more glucose, increasing uptake from blood)
3) converstion of glucose into glycogen in cells of liver and musckes
4) converstion of glucose -> fat
What does alpha cells detect
Fall in bgc
How do alpha cells respond to fall in blood glucose
Secrete glucagon directly into blood plasm
How does glucagon raise blood gc
1) Attach to specific protein receptors on cell-surface membrane of liver cells
2) Activate enzymes that convert glycogen to glucose
3) Activate enzymes that convert amino acids and glycerol -> glucose (gluconeogenesis)
Does adrenaline raise or lower bgc
Raise
How does adrenaline raise bgc
Attaches to protein receptors on cell-surface membrane of target cells
Activates enzymes to breakdown glycogen -> glucose in the liver
Describe what occurs if blood glucose concentration rises (hormones)
1) Detected by beta cells in pancreas which produces insulin
2) insulin will either:
-increase cellular respiration
-conversion of glucose -> glycogen
-converstion of glucose -> fat
-absorption of glucose -> cells
3) BGC falls back to optimum
Describe what occurs when bgc falls
1) Detected by alpha cells in pancrease to produce glucagon
2) glucagon either:
-converts glycogen to glucose
-converts amino acids to glucose
3) back to optimum
OR
2) uncontrolled quantity of glucose enters from intestine
3) BGC rises back to optimum
