6.8 Control of blood glucose concentration Flashcards
Decreasing BGC
• Receptors in the pancreas detect high BGC, causing beta cells in the islets of Langerhans to secrete insulin
• Insulin binds to specific receptors on cell membranes of liver/muscle cells
• This causes more glucose channel proteins to fuse with the cell membrane, increasing permeability to glucose
• So more glucose enters cell by facilitated diffusion
• This also activates enzymes involved in conversion of glucose to glycogen (glycogenesis)
• This establishes a concentration gradient so more glucose enters cell by facilitated diffusion
Increasing BGC
• Receptors in the pancreas detect low BGC, causing alpha cells in the islets of Langerhans to secrete glucagon
• Glucagon binds to specific receptors on cell membranes of liver cells
• This activates enzymes involved in conversion of glycogen to glucose (glycogenolysis) and amino acids/glycerol to glucose (gluconeogenesis)
• This establishes a concentration gradient so more glucose enters blood by facilitated diffusion
How does the second messenger model work?
• Adrenaline / glucagon attach to specific receptors on cell membranes of liver cells
• Activating adenylate cyclase
• Adenylate cyclase converts ATP into cAMP
• cAMP (a second messenger) activates protein kinase
• Protein kinase activates enzymes that break down glycogen to glucose (glycogenolysis)
Type I diabetes
Immune system destroys beta cells in the islets of Langerhans so not enough insulin produced
Controlled by injecting insulin and eating regularly to control carbohydrate intake
Type II diabetes
Receptors lose responsiveness to insulin (but insulin still produced)
Controlled by reducing sugar and fat intake, increasing exercise and losing weight
