Control of Blood Glucose Concentration
➢ Insulin and glucagon are secreted by the islets of Langerhans (clusters of cells) in the
pancreas.
➢ The pancreas has endocrine glands (glands with no ducts that secrete directly into
the blood) and exocrine glands (glands with a duct that secrete into a tube).
➢ Alpha cells secrete glucagon into the blood (think a for alpha and a in glucagon)
➢ Beta cells secrete insulin into the blood.
Key Words:
Glycogenesis: Conversion of glucose into glycogen; caused by insulin (when blood glucose
conc. is too high)
Glycogenolysis: Breakdown of glycogen into glucose; caused by glucagon (when blood
glucose conc. is too low)
Gluconeogenesis: Production of glucose from sources other than carbohydrates (when
supply of glycogen is exhausted)
Hypoglycemia: low blood glucose concentration
Hyperglycemia: high blood glucose concentration
When blood glucose concentration is too high:
➔ Insulin binds to specific glycoprotein receptors on cell membranes of liver cells
(hepatocytes) and muscle cells, and causes a change in the tertiary structure of the
glucose transport protein channels.
➔ The muscle cells take up more glucose by increasing the number of channel proteins
in the cell membrane (the muscle-cell membrane becomes more permeable to
glucose).
➔ Insulin activates enzymes in liver and muscle cells to convert glucose -> glycogen
(process= glycogenesis)
➔ Glycogen is stored in cytoplasm as an energy source.
➔ Insulin increases the rate of respiration of glucose.
When blood glucose concentration is too low:
➔ Glucagon binds to specific receptors on the cell membranes of liver cells and
activates enzymes in liver cells that break down glycogen -> glucose. (process=
glycogenolysis)
➔ Glucagon activates enzymes: glycerol + amino acids -> glycerol (formation of
glucose from non-carbohydrates= gluconeogenesis)
➔ Glucagon decreases the rate of respiration of glucose in cells.
Anything that involves glucose as the end product involves glucagon.
Removal of glucose= insulin
➢ Insulin and glucagon are secreted by the islets of Langerhans (clusters of cells) in the
pancreas.
➢ The pancreas has endocrine glands (glands with no ducts that secrete directly into
the blood) and exocrine glands (glands with a duct that secrete into a tube).
➢ Alpha cells secrete glucagon into the blood (think a for alpha and a in glucagon)
➢ Beta cells secrete insulin into the blood.
Key Words:
Glycogenesis: Conversion of glucose into glycogen; caused by insulin (when blood glucose
conc. is too high)
Glycogenolysis: Breakdown of glycogen into glucose; caused by glucagon (when blood
glucose conc. is too low)
Gluconeogenesis: Production of glucose from sources other than carbohydrates (when
supply of glycogen is exhausted)
Hypoglycemia: low blood glucose concentration
Hyperglycemia: high blood glucose concentration
When blood glucose concentration is too high:
➔ Insulin binds to specific glycoprotein receptors on cell membranes of liver cells
(hepatocytes) and muscle cells, and causes a change in the tertiary structure of the
glucose transport protein channels.
➔ The muscle cells take up more glucose by increasing the number of channel proteins
in the cell membrane (the muscle-cell membrane becomes more permeable to
glucose).
➔ Insulin activates enzymes in liver and muscle cells to convert glucose -> glycogen
(process= glycogenesis)
➔ Glycogen is stored in cytoplasm as an energy source.
➔ Insulin increases the rate of respiration of glucose.
When blood glucose concentration is too low:
➔ Glucagon binds to specific receptors on the cell membranes of liver cells and
activates enzymes in liver cells that break down glycogen -> glucose. (process=
glycogenolysis)
➔ Glucagon activates enzymes: glycerol + amino acids -> glycerol (formation of
glucose from non-carbohydrates= gluconeogenesis)
➔ Glucagon decreases the rate of respiration of glucose in cells.
Anything that involves glucose as the end product involves glucagon.
Removal of glucose= insulin
