Pancreas

• The pancreas functions in both an endocrine and exocrine way
• Type II diabetes can be treated with insulin supplements, diet, and careful monitoring
• Diabetes mellitus is a disease where the body cannot control blood glucose levels
• Risk factors for type II diabetes include obesity, high sugar diet, ethnicity, and sedentary lifestyle
• Endocrine function of the Islets of Langerhans

  Secreting insulin from beta cells and glucagon from alpha cells directly into the blood
• If blood glucose concentration is too high

  • Insulin is secreted by beta cells, inhibiting the action of alpha cells
  • Insulin travels to target cells in the liver, fat, and muscle cells
  • Binding of insulin to receptors on the plasma membrane causes adenyl cyclase to convert ATP into cAMP
  • cAMP activates enzyme-controlled reactions to stimulate the opening of glucose channels in the plasma membrane, causing more glucose to enter the cell and be converted to glycogen or fats for respiration
• Symptoms of diabetes include tiredness, thirst, and ketoacidosis
• Type II diabetes results from cells becoming less responsive to insulin as the affected person ages
• Type I diabetes is an autoimmune disease where beta cells are destroyed, leading to insufficient insulin production
• Alpha and beta cells

  • Contain many ribosomes and RER to efficiently manufacture protein hormones
  • Contain a large number of Golgi involved in packaging the hormones into vesicles
  • Hormones are secreted via exocytosis from secretory vesicles
  • Contain a large number of mitochondria for ATP production
• Blood glucose concentration needs to be kept in the correct range of about 90mg per 100cm3 of blood to ensure essential processes like respiration of brain cells are maintained
• People with diabetes can be treated with insulin produced by genetically engineered bacteria, reducing the risk of rejection and infection
• Control of insulin secretion

  1. Beta cells contain potassium and calcium ion channels

  2. Glucose diffuses into beta cells through specific channel proteins

  3. ATP is produced from glucose respiration, closing ATP-gated potassium ion channels

  4. Closure of potassium ion channels causes depolarisation, opening calcium ion channels allowing Ca2+ to enter the cell, causing vesicles containing insulin to fuse with the plasma membrane via exocytosis
• If blood glucose concentration is too low

  • Alpha cells secrete glucagon
  • Glucagon stimulates hepatocytes to convert glycogen into glucose (glycogenolysis)
  • Glucose diffuses out of hepatocytes into the blood
  • Cells use fatty acids and amino acids for respiration instead
• Exocrine function of the pancreas

  Secreting digestive enzymes such as amylase, trypsin, and lipase to the duodenum via the pancreatic tract
• Type I diabetes can be managed by monitoring blood glucose concentration and regular insulin injections
• Precursor pancreatic cells have been found in the pancreas of mice
• If a human equivalent of precursor pancreatic cells is found, it could be used to treat type I diabetes via the synthesis of new beta cells
• Other treatment options for diabetes include the use of stem cells
• Suffering from diabetes can be treated by insulin produced by genetically engineered bacteria
• Advantages of using genetically engineered organisms for insulin production

  • Possible to synthesise human insulin instead of treating with animal-derived versions
  • Lower chance of rejection and infection
  • Cheaper manufacturing compared to extraction from other animals