Lecture 29: Glucose Anabolism (Gluconeogenesis) Flashcards
Gluconeogenesis Overview
What type of precersors create glucose?
noncarbohydrate precursors
Gluconeogenesis Overview
What are the main precursors?
Lactate
AA
Glycerol
Gluconeogenesis Overview
Where in the body does gluconeogenesis primarily take place?
The liver
Gluconeogenesis Overview
When is gluconeogensis important?
During fasting and starvation
* when glucose cannot be obtained through fuel
** glucose is the primary fuel for the brain and only fuel for red blood cells
Gluconeogenesis Overview
Where does gluconeogenesis happen (cell wise)?
cytosol
mitrochondria
ER
Gluconeogenesis Overview
What is gluconeogensis in relation to glycolosis?
It opperates in the opposite direction to glycolosis but is not the reverse since glycolosis has 3 irreversible reactions that must be bypassed
Gluconeogenesis Overview
What does glyconeogenesis have to combat Hexokinase?
Glucose-6-phosphotase
Gluconeogenesis Overview
What does glyconeogenesis have to combat phosphofructokinase?
Fructose 1,6-biphosphotase
Gluconeogenesis Overview
What does glyconeogenesis have to combat pyruvate kinase?
pyruvate carboxylase and phosphoenolpyruvate carboxykinase
Bypass of Pyruvate Kinase
How many energy consuming steps are there in this section?
2
Bypass of Pyruvate Kinase
What is the first step?
Pyruvate carboxylase concerts pyruvate to oxaloacetate
Bypass of Pyruvate Kinase
Where does this step take place?
Inside the mitrochondria
Bypass of Pyruvate Kinase
How does oxaloacetate leave the mitochondria for use in step 2?
It cannot leave directly, it is shuttled out using malate
Bypass of Pyruvate Kinase
What does shuttled through Malate mean?
The oxaloacetate is reduced to malate to exit the mitochondia then oxidized back into oxaloacetate once in the cytosol (uses NADH and NAD)
Bypass of Pyruvate Kinase
What molecules are used to transform pyruvate to oxaloacetate?
CO2 and H2O
Bypass of Pyruvate Kinase
What cofactor is needed for any carboxylation?
Biotin
Bypass of Pyruvate Kinase
What is the second step?
Phosphoenolpyruvate caboxykinase converts ocaloacetate to Phosphoenopyruvate (PEP) via phosphorylation
Bypass of Pyruvate Kinase
Where does this step happen?
within the cytosol
Bypass of Pyruvate Kinase
What energy is used during step 2?
GTP
Bypass of Pyruvate Kinase
What is the summed reaction?
Pyruvate + ATP + GTP + H2O
–>
phosphoenolpyruvate + ADP + GDP + Pi + 2 H
Hydrolytic reactions bypass phosphofrucotkinase and Hexokinase
What do cells use to bypass kinases?
phosphatase
Hydrolytic reactions bypass phosphofrucotkinase and Hexokinase
What does phosphatase do?
hydrolyzes out the phosphate
Hydrolytic reactions bypass phosphofrucotkinase and Hexokinase
What does Fructose 1,6-biphosphatase do?
converts Fructose 1,6 -phosphate to Fructore 6-phosphate by removing a phosphate from the C1 position
Hydrolytic reactions bypass phosphofrucotkinase and Hexokinase
What type of enam is fructose 1,6-biphosphatase?
Allosteric, meaning it is oppositely regulated with PFK (if one is higher, the other is lower. This regulates if the cell is breaking down glucose or building it)
Hydrolytic reactions bypass phosphofrucotkinase and Hexokinase
What does glucose 6-phosphatase do?
hydrolyzes glucose-6-phosphate to glucose by removing the phosphate (mainly happens in liver)
Gluconeogenesis and glycolysis are reciprocally regulated
What is reciprocally regulated?
With these two pathways being opposite, only one is able to be running at a time to not form a futile cycle
Gluconeogenesis and glycolysis are reciprocally regulated
What is a futile cycle?
When both pathways, that have opposite effects, are simutaneously active in a cell and thus wasting energy
Gluconeogenesis and glycolysis are reciprocally regulated
Q from Lecture: Glycolysis yields how many high-energy phosphate bonds (ATP)?
2
Gluconeogenesis and glycolysis are reciprocally regulated
Q from Lecture: Gluconeogenesis expends how many high-energy phosphate bonds (ATP and GTP)?
6
Gluconeogenesis and glycolysis are reciprocally regulated
Q from Lecture: A futile cycle of both pathways would waste how many high-energy phosphate bonds per cycle (ATP and GTP)?
4
Gluconeogenesis and glycolysis are reciprocally regulated
What happens in the other pathway if one irreversible step is active in a pathway?
The matching opposite step in the other pathway is inhibited by the first
Gluconeogenesis and glycolysis are reciprocally regulated
When is each pathway active?
If ATP is required, glycolysis is active
If glucose is required, gluconeogenesis is active
