[16.3] hormones, regulation of blood glucose concentration Flashcards
what are hormones?
chemicals released from a specific gland which go to specific target cells, which have specific receptors on their cell, via the bloodstream
what determines whether or not a target cell is correct?
- whether it has the correct specifically shaped hormone receptors in the cell membrane
- correct tertiary structure means it is the target cell
what 3 hormones are involved in regulating blood glucose?
- glucagon
- insulin
- adrenaline
where is glucagon produced?
α cells in the islets of langerhans in the pancreas
larger
where is insulin produced?
β cells in the islets of langerhans in the pancreas
smaller
where is adrenaline produced?
adrenal glands
produced in emergency situations
which hormones use the second messenger model?
adrenaline and glucagon
describe the second messenger model of hormone action (7)
- X binds to a transmembrane protein receptor in the cell-surface membrane of a liver cell
- binding of X cases the protein to change shape inside the membrane
- change of protein shape leads to the activation of the enzyme adenyl cyclase
- activated adenyl converts ATP to cyclic AMP (cAMP)
- cAMP acts as a secon messenger that binds to protein kinase, changing its shape and therefore activating it
- active protein kinase enzyme catalyses the conversion of glycogen to glucose
- glucose moves out of the liver cell by FD and into the blood through channel proteins, thus increasing blood sugar levels
describe the sequence of events glucagon and adrenaline undergo to lead to a response
- S: blood sugar decreases
- R / C / E: α cells / adrenal glands
- R: blood sugar increases
what 3 important processes associated with regulating blood sugar take place in the liver?
- glycogenesis
- glycogenolysis
- gluconeogenesis
what factors lead to an increase in blood glucose concentration?
- glucose taken in from food
- glycogenolysis
- gluconeogenesis
how is glucose used which decreases its concentration in blood?
- respiratory substrate
- excess undergoes glycogenesis
- excess is converted into lipids or proteins if nitrogen is added in the liver
what is glycogenesis?
conversion of glucose into glycogen
what is glycogenolysis?
breakdown of glycogen into glucose
what is gluconeogenesis?
production of glucose from other sources eg. breakdown and conversion of lipids / proteins
why does blood glucose concentration need to be regulated?
- glucose is a respiratory substrate so it provides energy so must be kept relatively constant
- low conc = cells are deprived of energy and die
- too high = blood water potential lowers which creates osmotic problems
describe the sequence of events insulin undergoes to lead to a response
- S: blood sugar increases
- R / C / E: β cells in pancreas
- R: blood sugar decreases
what happens when insulin combines with the specific receptors? (3)
- glucose transport carrier proteins change tertiary structure so they change shape and open, allowing more glucose into cells by FD
- more vesicles fuse with the cell-surface membrane so there are more glucose transport channels
- enzymes that convert glucose into glycogen and fat are activated
how does insulin’s actions lead to a decrease in blood glucose concentration? (4)
- increased rate of absorption of glucose in cells, especially muscle cells
- increased respiratory rate of cells, so they take up more glucose from the blood
- increased rate of glycogenesis (glucose -> glycogen) in cells of liver and muscles
- increased rate of conversion of glucose into fat
what does glucagon do? (3)
- attach to specific protein receptors on the cell-surface membrane of liver cells
- activate enzymes that convert glycogen to glucose
- activate enzymes involved in the conversion of AAs and glycerol into glucose (gluconeogenesis)
what does adrenaline do to increase blood glucose concentration?
- attach to protein receptors on the cell-surface membrane of target cells
- activate enzymes that cause the breakdown of glycogen to glucose in the liver (glycogenolysis)
