Lecture 62 "Insulin & Glucagon"
Terms
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- other neurotransmitters and hormones that have the same function as glucagon (3)
-
catecholamines (NE, Epi)
GH
glucocorticoids (cortisol)
*released in times of stress (e.g., exercise, illness)* -
delta cells
*location
*synthesize (2) -
disperesed in islets of Langerhans' periphery
somatostatin
gastrin -
F cells
*location
*synthesize -
periphery of islets of Langerhans
pancreatic polypeptide (gastrointestinal hormone) - stimulators of glucagon secretion (4)
-
hypoglycemia (bg <50 mg/dL)*most important*
increase in Arg and Ala (indicates protein degradation)
sympathetic stimulation (e.g., exercise)
stress (e.g., healing after surgery) - T/F glucagon circulates in the blood bound to carrier proteins
- False
- inhibitors of glucagon secretion (3)
-
somatostatin *most important*
insulin
hyperglycemia (bg >200 mg/dL) - effects of glucagon on the liver (4)
-
glycogenolysis (glycogen --> glucose)
gluconeogenesis (amino acids --> glucose)
lipolysis (TG's --> FA's --> glycerol --> glycerol-phosphate --> glucose)
ketogenesis - effects of glucagon on adipose tissue (2)
-
decreased glycolysis
increased lipolysis (release of FA's) - levels of cAMP vs. glucagon and insulin
-
glucagon increases cAMP
insulin decreases cAMP - in hepatocytes, glucagon _______ glycogenolysis and ______ glycogen synthesis by ______ cAMP
-
stimulates
inhibits
increasing - in hepatocytes, insulin _______ glycogenolysis and ______ glycogen synthesis by _________ cAMP
-
inhibits
stimulates
decreasing - cAMP controls the production of
- fructose 2,6-bisphosphate
-
glycolysis:
cAMP catalyzes the phosphorylation of ______ thereby _____ it -
pyruvate kinsase
inactivating - function of pyruvate kinase
- converts PEP to pyruvate
- _______ is the principal competitor of gluconeogenesis
- lipogenesis
-
lipogenesis:
cAMP catalyzes the phosphorylation of ______
thereby ______ fatty acid synthesis (lipogenesis) -
acetyl CoA carboxylase (catalyzes the carboxylation of acetyl CoA to malonyl-CoA)
inhibiting - long chain fatty acids must be linked to ______ in order to cross the mitochondrial membrane
- carnitine
- carnitine acyl transferase is inhibited by
- malonyl-CoA
-
fatty acid oxidation & ketogenesis:
when fatty acid synthesis is inhibited (i.e., no ______) ________ is activated and fatty acid oxidation and ketogenesis occur -
malonyl-CoA
carnitine acyl transferase - ________ and ______ are formed from the condensation of 2 acetyl CoA molecules
-
acetoacetate
beta-hydroxybutyrate - Fructose 2,6-bisphosphate activates ________and inhibits _________, therby favoring glycolysis
-
phosphofructo-kinase (PFK)
fructose-1,6-bisphosphatase - fructose-2,6-bisphosphate is formed by the enzymes (2)
-
F-2,6-kinase
F-2,6-phosphatase - glycolysis occurs when fructose-6-phosphate is _____ than fructose-2,6-bisphosphate
- <<
- glucagon stimulates a(n) ______ in cAMP, thus activating _____
-
increase
PKA - PKA phosphorylates ______, which converts it to ______
-
fructose-2,6 kinase
fructose-2,6 phosphatase - when fructose-2,6-bisphosphate is depleted ______ is blocked and _____ decreases
-
PFK
glycolysis - gluconeogensis if favored when _______ activity increases and _______ is convereted to __________
-
fructose 1,6-bisphosphate phosphatase
fructose-1,6-bisphosphate
fructose-6-phosphate - after a meal stimulators of insulin secretion (4)
-
increased serum glucose
increased serum amino acids (Arg & Lys)
increased serum free fatty acids
increased serum ketone bodies (keto-acids) - hormone stimulators of insulin secretion (7)
-
GIP
glucagon
gastrin
CCK
secretin
VIP
Epi (beta receptor)
*hormones that are elevated in the presence of food* - neuronal stimulator of insulin secretion
- PNS ("Rest & Digest")
- "starvation" inhibitors of insulin secretion (3)
-
decreased serum glucose
decreased serum amino acids
decreased free fatty acids - hormone inhibitors of insulin secretion (2)
-
somatostatin
Epi (alpha receptor) - increased entrance of glucose into the cell stimulates ________ leading to an increase in ______
-
glycolysis
ATP - increased _____ inhibits an ATP-sensitive ______
-
ATP
K-channel - Inhibition of an ATP-sensitiive K-channel causes membrane ______
- depolarization
- membrane depolarization activates a _________
- voltage-gated Ca-channel
- activation of a Ca-channel promotes Ca influx, which increases [Ca] and evokes ________
- Ca-induced Ca release
- elevated Ca leads to exocytosis and release of ______ into the bloodstream
- insulin
- Na-dependent secondary active glucose transporter located in the intestine and kidney
- SGLT-1
- facilitated diffusion glucose transporter located in the liver and pancreas
- GLUT-2
- glucose transporter which moves from the cytosol to plasma membrane in the presence of insulin
- GLUT-4
- major site of insulin-mediated glucose uptake
- skeletal muscle (80%)
- in the liver, insulin stimulates (5)
-
glucose uptake
glycogenesis
glycolysis (supplies acetyl CoA for lipogenesis)
fatty acid synthesis (lipogenesis)
protein synthesis - in the liver, insulin inhibits (6)
-
glycogenolysis
gluconeogenesis
fat oxidation
ketogenesis
proteolysis
urea cycle - in skeletal muscle, insulin stimulates (5)
-
glucose uptake (GLUT-4)
glycogenesis
glycolysis (provides acetyl CoA for lipogenesis)
amino acid uptake
protein synthesis - in skeletal muscle, insulin inhibits (2)
-
glycogenolysis
proteolysis - in adipose tissue, insulin stimulates (5)
-
glucose uptake (GLUT-4)
glycolysis (alpha-glycerol phosphate)
production of alpha-glycerophosphate
esterifcation of fats
synthesis of lipoprotein lipase - in adipose tissue, insulin inhibits (1)
- lipolysis