L16 Flashcards
Effect of Insulin and Glucagon on the synthesis of glycolysis enzymes
insulin induces production of hexokinase, phosphofructokinase, and pyruvate kinase. glucagon represses their production.
beta cells of pancreas produce _____ and _____
insulin and amylin
delta cells of pancreas produce ____ and ____
gastrin and somatostatin
F cells of pancreas produce ______
pancreatic polypeptide
explain mechanism of glucose-facilitated insulin release
glucose enters beta cell through GLUT2. creates ATP through glycolysis and the ATP closes the ATP-sensitive K+ channel. More K+ in the cell causes depolarization which opens the voltage-gated Ca2+ channel. The influx of calcium stimulates exocytosis of vesicles with insulin.
where in the body are excess fuels stored?
hepatocytes, adipocytes & skeletal muscle
insulin’s functions
– increases anabolism & synthesis of storage molecules
– decreases catabolic or breakdown reactions
– promotes entry of glucose & amino acids into cells
– stimulates phosphorylation of glucose
– enhances synthesis of triglycerides
– stimulates protein synthesis along with thyroid & growth hormone
amino acids ______ insulin release
stimulate
The major transporter for uptake of glucose is _______
GLUT4
how does insulin stimulate uptake of glucose?
GLUT4 is translocated to the plasma membrane through the action of insulin. Insulin stimulates the fusion of GLUT4 vesicles with the plasma membrane. When blood levels of insulin decrease, the GLUT4
transporters are recycled back into the cytoplasm.
GLUT1 and GLUT3 (Km ~ 1 mM) maximize glucose uptake in _________ and _________, respectively
erythrocytes; brain
where is GLUT2 found and how does it work?
Occurs in liver and pancreatic b-cells. Has a high Km for glucose (~ 60 mM), so uptake varies with [glucose]
the parasympathetic NS stimulates [insulin/glucagon] secretion
insulin
Insulin promotes glycogen storage, by promoting ____________
dephosphorylation
how does insulin stimulate glycogen synthesis?
it dephosphorylates glycogen synthase, activating it. also activates protein phosphatase-1.
mechanism of glucagon action
Gs GPCR –> cAMP –> PKA
also activates IP3 –> Ca2+
main target tissues of glucagon
liver, muscle, adipose tissue
stimulants of glucagon secretion (4)
- Decreased [ glucose ]
- Increased [ free aa ]
- Adrenaline (Sympathetic NS)
- Secretin
effects of glucagon
3 major sources of blood glucose
- glycogen breakdown in liver produces glucose
- glycerol from adipose converted by liver into glucose
- gluconeogenesis using amino acids produces glucose
without glucose, most body tissue can switch to utilizing fatty acids,
except ____
the brain still needs glucose
how do glucagon and epinephrine work together?
epinephrine stimulates glycogen breakdown in muscle and liver
glucagon does same mostly in liver
they also trigger the phosphorylation of glycogen synthase which inactivates it and prevents glycogen formation
glycogen phosphorylase needs to be ________ to stimulate glycogen ________
phosphorylated; degradation
glycogen synthase needs to be _______ to stimulate glycogen _______
dephosphorylated; synthesis
amylin acts like ______
GLP-1
Abnormalities due to insulin deficiency
- hyperglycemia
- increased lipolysis
- acidosis
- high LDL, low HDL
- Osmotic diuresis, plasma hyperosmolarity, dehydration, hypovolemia, polydipsia
- depletion of intracellular and whole-body K+
diabetic ketoacidosis
potentially life-threatening complication of diabetes, body lacks insulin for glucose uptake so it burns fat instead for energy, leading to a buildup of ketones and a dangerous increase in blood acidity.
Elevated levels of glucose accelerate the formation of __________
advanced glycation end-products (AGEs)
why are advanced glycation end products bad?
harmful because they accumulate in the body and receptors (RAGE), leading to oxidative stress, inflammation, and damage to tissues and organs, potentially contributing to chronic diseases and accelerated aging.
what is the Cori cycle?
The Cori cycle, also known as the lactic acid cycle, is a metabolic pathway where lactate, produced by active muscles during intense exercise, is transported to the liver, converted back to glucose, and then returned to the muscles for energy
