hormonal communication

• endocrine glands - group of cells that secrete hormones directly into blood capillaries
• exocrine glands - secretes molecules into ducts
• examples of non steroid hormones

  • adrenaline
  • noradrenaline
  • insulin
  • ADH
• first messengers bind to a receptor on the cell surface membrane causing the release of a second messenger inside the cell, they often act via a G protein
• second messengers stimulate a change in the activity of the cell. in many cases the enzyme adenylyl cyclase is an effector molecule that converts ATP into cyclic amp which is the second messenger
• examples of steroid hormones

  • oestrogen
  • testosterone
  • aldosterone
  • glucocorticoids
  • androgens
• steroid hormones pass directly through the cell surface membrane and hind with a specific receptor in the cytoplasm. this enters the nucleus of the cell and acts as a transcription factor either promoting or inhibiting the synthesis of the gene
• adrenal cortex secretes steroid hormones
• adrenal medulla secretes non-steroid hormones
• pancreas

  • exocrine function - pancreatic juice is released from the cells and secreted into the tubules at the centre of the group, these join to form intralobular ducts which form the pancreatic duct and then the duodenum
  • endocrine function - the alpha cells in the islets of langerhans release glucagon, the beta cells release insulin
• regulation of insulin levels

  1. k channels in the plasma membrane are open and k diffuses out giving resting potential of -70mv
  2. glucose enters through glucose transporter proteins
  3. glucose is phosphorylated by glucokinase, producing ATP
  4. k channels are ATP sensitive and so close when levels are high
  5. as a result k cannot diffuse out bringing the potential to -30mv
  6. voltage gated calcium ion channels open
  7. calcium ions cause vesicles containing insulin to move and fuse with the membrane
• glycogenolysis - glycogen broken down into glucose in liver
• gluconeogensis - production of glucose from amino acids
• glycogenesis - glucose converted into glycogen
• type 1 diabetes

  • beta cells unable to produce insulin
  • autoimmune response
  • no cure
• type 2 diabetes

  • cannot use insulin effectively
  • there are treatments available
• advantages of using GM bacteria to produce insulin

  • no allergic reactions
  • higher quantities produced
  • cheaper production costs
  • ethics