25 Regulation of blood glucose levels by pancreas Flashcards
what happens in the absorptive state
ingested nutrients enter blood from GI and support energy requirements of body
excess nutrients are STORED to use in post absorptive state
what happens in post absorptive state
no nutrients are entering blood from GI
net catabolism of stores happens
post absorptive state must maintain blood glucose levels in absence of absorption
how do cells make ATP
using carbon sources - glucose etc
what is glucose mainly used fro in absorptive state
- used for energy
- storage as glycogen in liver and skeletal
- storage as fat in adipose
what is the only organ that can produce glucose in PA state
the liver
how does liver produce glucose
via gluconeogenesis and glycogen breakdown
what is essential for regulation of blood glucose
insulin – as glucose increases so does insulin
what do pancreatic islets do
contain cells that secrete insulin and glucagon
what cells do islets have
alpha and beta cells
what do alpha and beta cells secrete
alpha produce glucagon
beta produces insulin
are glucose and insulin peptide or steroid hormones
peptide
what does increase stimulate in liver, skeletal muscle and adipose
- increased glucose uptake
- increased glycolysis
- increased glycogen synthesis (liver and skeletal)
what does insulin inhibit in liver
- inhibit gluconeogenesis
- inhibit glycogen breakdown
what does insulin inhibit in skeletal muscle
glycogen breakdown
how does glucose regulate insulin release from beta cells
- increased uptake and metabolism of glucose leads to increase in ATP:ADP ratio
- increased ATP:ADP leads to CLOSURE of ATP-sensitive K+ channels and membrane depolarisation
- depolarisation of membrane leads to opening of voltage gated Ca2+ channels
- regulating increase in cytosolic Ca2+ promotes secretion of insulin via exocytosis of insulin granules
what happens when ATP binds to ATP-sensitive K+ channels
it closes the channel and leads to higher K+ in the cell
activation of protein kinase B steps
- insulin binds to insulin receptor (IR) and leads to auto receptor phosphorylation
- phosphorylated residues on IR act as binding sites for IR substate (IRS) proteins
- IR phosphorylates IRS proteins
- phosphoinositide 3-kinase binds to phosphorylated residue on IRS proteins and the converts the membrane lipid PIP2 into PIP3
- binding to PIP3 activates PDK1 which phosphorylates and activates PKB
- activated PKB mediates many of the intracellular effects of insulin
what is a key output of insulin binding
activation of protein kinase
what do kinases do
add phosphate to proteins
what are insulins important targets
liver, skeletal muscle and adipose tissue
how does insulin stimulate glucose uptake into skeletal muscle and adipocytes
by increased amounts of GLUT4 at the cell surface
what is a key step in regulating insulin stimulated GLUT4 vesicle exocytosis
protein kinase B activation
is anything soluble at the surface released during exocytosis
yes
what is the activity of glycogen synthase regulated by
phosphorylation
glycogen synthase is phosphorylated by GSK and made inactive
