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Homeostasis-glucose
AQA A-level biology regulation of blood glucose homeostasis year 13
| Term | Definition |
|---|---|
| 2nd messenger model | Intracellular molecules which cause physiological changes triggered by extracellular molecules binding to receptors at the cell surface |
| Adrenaline 2nd messenger model: Step 1 | Adrenaline binds to transmembrane protein receptor within the cell-surface membrane of a liver cell |
| Adrenaline 2nd messenger model: Step 2 | The binding of adrenaline causes a conformational shape change in the protein on the inside of the membrane |
| Adrenaline 2nd messenger model: Step 3 | On the bottom of this protein is an inactive adenyl cyclase which activates when the protein changes shape, this catalyses the conversion of ATP to cAMP |
| Adrenaline 2nd messenger model: Step 4 | The cAMP acts as the second messenger and binds to a protein kinase, causing a conformational shape change & a protein cascade which catalyses the conversion of glycogen to glucose which enters the blood stream through facilitated diffusion |
| Islets of Langerhans (α & β cells) | Groups of hormone producing cells scattered throughout the pancreas. α cells produce glucagon while β cells produce insulin into blood plasma |
| Glycogenesis | Conversion of glucose to glycogen using insulin |
| Glucogenolysis | Hydrolysis of glycogen back to blood glucose using |
| Gluconeogenesis | Production of glucose from non-carbohydrate sources such as glycerol & some amino acids |
| Effects of insulin | Changes shape of glucose transport carriers to open, vesicles containing glucose carriers (GLUT4) bind with cell membrane, activates enzymes that convert glucose into glycogen & fat, & increases cellular metabolism |
| Effects of glucagon | Activates enzymes which convert glycogen to glucose as well as causing gluconeogenesis from alternative respiratory substrates |
| Type I diabetes (insulin dependent) | Due to the body being unable to produce sufficient insulin, normally develops in childhood due to an immune response against β cells in the Islets of Langerhans preventing insulin production |
| Type II diabetes (insulin independent) | Glycoprotein receptors on liver or muscle cells become lost or insensitive to insulin, that or just insufficient insulin from pancreas for the amount of glucose consumed. Occurs generally due to poor lifestyle factors |
| Symptoms of diabetes (at least 4) | High blood-glucose concentration, glucose in urine, excessive urination, fatigue, increased hunger & thirst, genital yeast infection, unintentional weight loss, & blurred vision |
| How type I diabetes is controlled | Regular injections of insulin, must be injections as insulin is a peptide & would be digested if taken orally |
| How type II diabetes is controlled | Regulating intake of carbohydrates & exercising. Some drugs can be taken such as synthetic insulin, a drug which stimulates the pancreas, or a drug which inhibits glucose absorption in the small intestine |
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