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25 Cards in this Set

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  • Back
Where does the majority of Gluconeogenesis take place? Where else does Gluconeogenesis take place?
90% in liver, 10% in kidney
Steps of gluconeogenesis
pyruvate  Oxaloacetate (OAA) – Carboxylation by pyruvate carboxylase need coenzyme Biotin and 1 ATP; OAA  malate (need NADH) which then crosses mitochondrial membrane into Cytosol; malate to OAA (produce NADH); OAA to PEP by PEP Carboxykinase; to 2-phosphoglycerate to 3 Phosphoglyceride (use 1 ATP) to glyceraldehyde3P to fructose 1,6 Bisphosphate; to fructose 6 phosphate by fructose 1,6 Bisphosphate; to glucose 6 phosphate to glucose by glucose 6 phosphatase
Rate limiting enzyme of Gluconeogenesis
1) PEP Carboxykinase
2) pyruvate carboxylase
3) fructose 1,6 Bisphosphate
4) glucose 6 phosphatase
Where is Pyruvate Carboxylase found?
Liver and kidney mitochondria and found in muscle cells
What intermediate molecule that is also involved in the TCA is created during the conversion of Pyruvate to PEP?
Which TCA molecule is used solely as a transporter?
How is Biotin bound to Pyruvate Carboxylase? (In general, Carboxylase enzymes have Biotin as a cofactor; of course there are a few exceptions).
Covalently bound to the enzyme protein by the epsilon amino group of lysine
What is Biocytin?
covalently bound biotin
Acetyl CoA is an Allosteric activator of Pyruvate Carboxylase. Why would an increased amount of Acetyl CoA activate Pyruvate Carboxylase?
It is a high energy indicator so if you have a lot of it, its going to cause the reaction to go in the opposite direction and towards Gluconeogenesis
Where does Oxaloacetate (OAA) form? Where is it transported to? How is it transported?
a. It is formed in the mitochondria and gets transported to the Cytosol
b. It has to convert to malate by mitochondrial malate DH to cross the membrane; once in the Cytosol it gets converted back to OAA by cytosolic malate DH and produces NADH
What enzyme converts Fructose 1, 6-BP back to Fructose 6P? What inhibits this enzyme? What activates this enzyme? (Hint: There are various energy metabolites that affect the work of this enzyme and there are also allosteric regulators that affect the work of this enzyme; KNOW BOTH!)
a. Fructose 1,6-bisphosphotase does the conversion
b. It is inhibited by high levels of AMP which signals an energy poor state; and high levels of ADP; also inhibited by fructose 2,6-bisphosphate
c. It is activated by high levels of ATP and low levels of AMP
Which enzyme helps you bypass the irreversible Hexokinase reaction? Where is this enzyme found? (again: it’s not found everywhere, so be specific)
a. Glucose 6-phosphatase and glucose 6-phosphate Translocase which transports enzyme across rER
b. It is only found in the liver and Kidneys
Why can the muscle not create glucose via Gluconeogenesis?
Muscle lacks glucose 6-phosphatase
How much Energy is used up in creating one molecule of glucose?
4 ATP, 2 NADH, and 2 GTP
What effect does a lack of Fructose 2, 6-Bisphosphate have on the speed of Gluconeogenesis?
it'll speed it up, since it inhibits
What are the 3 most important sources of Gluconeogenic precursors?
a. Glycerol
b. Lactate
c. Pyruvate
37. How is Glycerol used to create glucose? (Specifically: Where does it come from? What reactions are performed on it?)
Released into the blood by exercising skeletal muscle and by cells that lack mitochondria; Cori cycle- glucose is converted to lactate by exercising muscle which diffuses into the blood. It is then taken up by the liver and reconverted to glucose.
How is alpha-Ketoacids used to create glucose? (Specifically: Where does it come from? What reactions are performed on it?)
Derived from hydrolysis of tissue proteins; OAA and alpha Ketoglutarate are derived from metabolism of Glucogenic amino acids; these substances can enter the TCA and form OAA, a direct precursor to PEP;
What is the Cori cycle? Where does glucose flow through? (Basically draw out the Cori cycle and remember it!)
Cori cycle- glucose is converted to lactate by exercising muscle which diffuses into the blood. It is then taken up by the liver and reconverted to glucose and then sent back to the exercising muscles;
What are ‘Ketogenic’ compounds? (be general; what molecule would create Ketogenic compounds)
Acetyl CoA and compounds that give rise to Acetyl CoA can’t give rise to net synthesis of glucose b/c irreversible nature of pyruvate DH reaction (pyruvate to A CoA), so instead these give rise to ketone bodies
How is Gluconeogenesis regulated on a minute-by-minute basis? (Specifically, what molecule is present to regulate this pathway?)
Glucagon and availability of gluconeogenic substrates
Glucagon performs 2 actions to affect the rate of Gluconeogenesis? One is related to levels of F-2,6BP and the other is related to regulation of activated levels of Pyruvate Kinase. Explain these two phenomenons. How would these regulatory events be affected if there was a sudden elevation of Glucagon in the blood?
a. glucagons lower level of F2,6BP which results in activation of F1,6bisphosphatase and inhibition of Phosphofructokinase
b. elevates cAMP levels, which increases Phosphorylation of pyruvate kinase (making it inactive) so higher PEP levels forced to Gluconeogenesis pathway
Effect of insulin
slows gluconeogenesis
What second messenger system is utilized by Glucagon to control the activity of Pyruvate Kinase?
Why is hepatic Pyruvate Carboxylase activated by Acetyl CoA in a starvation state?
Need glucose in blood for brain function; fatty acids are metabolized increasing levels of acetyl CoA through beta oxidation of these free fatty acids