13: Pancreatic Hormones- Schmidt Flashcards
3 things made from the insulin gene
a chain
b chain
c-peptide
formation of insulin from proinsulin precursor assures that A and B chain are always present in equal amounts
why is the presequence in the insulin gene important?
send the product to the ER, then it can be cleaved
where does proinsulin become insulin?
in the golgi
describe familial hyperproinsulinemia
defects in insulin processing due to mutations in insulin gene lead to high proinsulin levels in the blood
normal glucose metabolism still happens
describe insulin release
glucose is taken in by the cell, phosphorylated and metabolized to make ATP
ATP inhibits K+ channels and increases Ca2+ channels
rising intracellular calcium stimulates the release of insulin vesicles to the PM and insulin release
____ step of insulin production is influenced by glucose
every!
increase: transcription* initiation BRP-VP interaction elongation
decrease:
degradation
describe the insulin receptor
tetrameric
heavily glycosylated
7 h half life
autophosphorylative
what is the “paradox” of insulin binding to its receptor?
receptor activation leads to phosphorylation of signaling prtns and dephosphorylation of metabolic enzymes
“endocytosis of insulin-receptor complex”
what is the end effect of stimulating the insulin receptor?
translocation of GLUT4 to cell membrane
more detailed effects of insulin (4) and big effect (1)
- increased formation of glcogen
- increased uptake of glucose
- increased utilization of glucose
- decreased formation of glucose from glycogen, fat and protein
1**decreased blood glucose
decreased insulin sensitivity and inadequate secretion during preggers
gestational diabetes mellitus
insulin sensitivity of the mother decreases to provide glucose to the fetus
there is decreased insulin receptor kinase activity in GDM
synthesized in the alpha cell of pancreatic islets
glucagon
in contrast to insulin, glucagon does not contain disulfide bridges
look at slide 15
compares insulin and glucagon
where does glucagon have an effect?
ONLY IN THE LIVER (inactivates glycogen synthetase, activates glycogen phosphorylase, activates glucose6phosphatase, activates gluconeogenesis)
no receptors on muscle or adipose tissue
look at slide 16
stimulants for insulin and glucagon release
