Flashcards in Test 4 Deck (21):
Where do Gluceogenesis occur in humans?
Purpose of Glucose
-used for energy storage
-serves as a precursor for 5 carbons sugars (ribose and deoxyribose) used in nucleic acids
Describe the transport mechanism to bring lactate from the muscle to the liver
since the muscle does not carry out gluceoneogenesis
-lactate is transported out of the muscle, through the blood, and transported into the liver where it can be used in gluceoneogenesis
-process called the cori cycle
-synthesis of glucose in the liver
-transfer of glucose to muscle where it is used for ATP
-Transport of lactate back to liver where it is used for gluceoneogenesis
Where doe the regulatory enzyme ATP work?
inhibits glycolysis at the enzyme PFK-1 and Pyruvate Kinsae
Where doe the regulatory enzyme Citrate work?
inhibits glycolysis at the enzyme PFK-1
Where does the regulatory enzyme AMP work?
activates glycolysis at the enzyme PFK-1
inhibits gluceoneogenesis at the enzyme Fructose 1,6-phosphatase
Where does the regulatory enzyme Fructose 1,6-bisphosphate work?
activates glycolysis at the enzyme Pyruvate Kinase
-feed forward activation
Where does the regulatory enzyme Acetyl-CoA work?
activates gluceoneogenesis at the enzyme pyruvate carboxylase
What is a very important allosteric regulatory in Glycolysis and gluceogenesis?
-induces the glycolysis pathway by activating PFK-1
-at the same time it suppresses the gluceogenesis pathway by inhibiting the enzyme fructose 1,6-bisphosphatase
PKA involvement in gluceogenesis and glycolysis
-the enzyme pyruvate kinase is inhibited by phosphorylation carried out by the kinase PKA
-occurs in the liver, kidney, and small intestine
The UDP glucose is then synthesized by the glycogen synthase to make glycogen
glycogen is reacted with Pi by the enzyme polysaccharide phosphorylase to produce glucose 1-phosphate
secreted by the pancreas in response to low blood glucose levels
-role is to induce gluconeogenesis
How does Glucagon induce gluceogenesis?
binds to receptors in the liver that activate cAMP synthase
-cAMP synthase activates PKA
-phosphorylates pyruvate kinase and inhibits it, inhibiting the last step of glycolysis
-results in phosphorylation of glycogen phosphorylase-activating it- which results in synthesis of Glucose 1-phosphate from glycogen
-phosphorylates glycogen synthase which it inhibits it and no more glycogen is made
-activates phosphoprotein phosphatase-1
Liver cells and glucagon
glucagon raises glucose concentration by producing glucose from glycogen and blocking glycogen resynthesis
Liver cells and insulin
insulin lowers glucose concentration by activating glycogen synthesis and blocking glycogen phosphorolysis
Why do other cells not have an effect on glucagon
these cells do not have glucagon receptors.
Instead muscle, adipocytes, and the heart respond to epinephrine to raise glucose concentration