Gluconeogenesis Flashcards
What is gluconeogeneis
What else can be made
Going from pyruvate to glucose
Other molecules can be made from the the intermediate of this reaction like lactate, amino acids, glycerols
Where does gluconeogensis mainly happen
In the liver
What are all of the steps of gluconeogenesis
Same as glycolysis just backwards
But after phosphoenol pyruvate, phosphoenol pyruvate carboxy kinase makes oxaloacetate
Oxaloaceetate turns into pyruvate through pyruvate carboxylase
But this is all backwards remember, so oxaloacetate is actuallly formed
What reactions in gluconeogensis turn GTP to gdp and atp to adp
Pyruvate to oxaloacetate turns atp to adp
Oxaloacetate to phosphoenol pyruvate turns GTP to gdp
3-phosphoglycerate to 1,3 biphosphoglycerate turns atp to adp
Is gluconeogensis the exact reverse of glycolysis
No, the energy used and released to both reactions is not the same
The three irreversible reaction in glycolysis need to be bypassed in gluconeogeneis
What are the 3 differences in gluconeogensis compared to glycolysis
Pyruvate to phosphoenol pyruvate occurs in 2 steps instead of one (pyruvate to oxaloacetate then to phosphoenol pyruvate)
Fructose 1 6 bisphosphate to F 6 phosphate uses fructose 1,6 bisphosphatase instead of pfk
G 6 p to glucose uses glucose 6 phosphatase instead of Hexokinase
What enzyme turns pyruvate to oxaloacetate, where, and how
Pyruvate carboxylase
This step happens in the mitochondrial matrix
Carboxyl action happens in three steps
What is the first step of how pyruvate turns to oxaloacetate
The cofactor bicarbonate (HCO3-) is activated by atp to make carboxyphosphate
What is the second step of how pyruvate turns to oxaloacetate
The pyruvate carboxylase enzyme has a biotin conpapent
The previously made carboxyphosphate bind to this part of the enzyme to make the co2-biotin-enzyme
What is the third step of how pyruvate turns to oxaloacetate
the newly made co2-biotin-enzyme transfers a CO2 to the pyruvate to form oxaloacetate
The biotin enzyme is reformed to made more oxaloacetate
How many domains does pyruvate carboxylase have
4
The three step reaction happens at each domain
What enzyme turns oxaloacetate to phosphoenol pyruvate and how
phosphoenol pyruvate carboxy kinase
It hydrolyzes GTP to gdp to decarboxylate oxaloacetate
This make the less stable enol isomer which then gets a phosphate added to it to trap it in that form
In the first two steps of gluconeogensis to go from pyruvate to phosphoenol pyruvate, how much atp and GTP is used
1 atp and 1 GTP but it’s hapoens two times so 2 atp and 2 GTP
Is something is decarboxylated, what happens after
Phosphorylation
This is a pattern that happens in metabolism
Pyruvate turns to oxaloacetate in the
What happens after this and why
Mitochondria
The oxaloacetate gets reduced to malate through the use of NADH (still in mitochondria) and malate degyhydrogenase
This is because the oxaloacetate can’t leave the mitochondria in its current form
After malate is formed what happens
Why
It’s moved out of the mitochondria to the cytoplasm
The malate outside the mitochondria then gets oxidized back to oxaloacetate and also makes NADH
The Cytosiloc Nadh is used in gluconeogensis
F 16 pisphopahte to F 6 phosphate
G 6p to glucose
How are they different in gluconeogensis
They are important a regulations step and they each have H2O added to form them
What does it means that gluconeogensis and glycolysis are regulated reciprocally?
Why
When one process is highly active, the other is inhibited
Because is both happen at the same time, no net atp or GTP is actually being made
How is reciprocal regulation done for the pfk in glycolysis and the fructose 1,6 bisphopsphatase in gluconeogensis
In gluconeogensis, the important regulation enzyme is fructose 1,6 bisphosphatase not PFK
It is reciprocal to pfk,
if pfk is activated by amp and F 26 bp, then fructose 1,6 bisphosphatase is inhibited by it.
If there’s low atp (more amp) glycolysis is needed and gluconeogensis is inhibited
If there more glucose, there more F 2 6 bp. If more F 26 bp, more glycolysis and less gluconeogensis
If there’s high citrate (from TCA) or H there’s high energy charge (atp) and pfk if inhibited, so glycolysis is inhibited and gluconeogensis is activated.
How is reciprocal regulation done for the pyruvate kinase in glycolysis and the three step reaction to make phosphoenol pyruvate in gluconeogensis
If there’s high adp/amp, energy is needed and gluconeogensis is inhibited (because it uses energy to make glucose)
If there’s high atp and alanine there’s higher energy charge, if there’s more energy pyruvate kinase is inhibited (don’t need to make more energy)
What forms the fructose 2,6 bisphopshate that inhibits fructose 1 6 biphosphatase
What forms the fructose 6 phosphate
Phosphofructokinase 2 makes fructose 2,6 bisphopshate
Fructose biphosphatase 2
Phosphofructokinase 2, Fructose biphosphatase 2 make up the enzyme fructose 1,6 biphosphatase
What type of enzyme is fructose 1,6 biphosphatase what does this mean
Those two domains exist as a single polypeptide (fructose 1,6 biphosphatase)
It’s a bifunctional enzyme and these two domains is how it’s regulated
When one domain is active, the other is inactive
In the state of the fructose 1,6 biphosphatase enzyme where pfk 2 is phosphorylates what happens
If pfk 2 is phosphorylated, it’s inactive.
This makes the fbp 2 active
This means that fructose 2,6 bp is not made, so glycolysis is inhibited and gluconeogensis does happen
In the state of the fructose 1,6 biphosphatase enzyme where pfk 2 is dephosphorylated what happens
Pfk 2 is active so the fructose bisphosphatase is inactive
This means that fructose 2 6 bisphosphate is made and glycolysis is stimulated, gluconeogensis is inhibited.
This happens when more glucose
How is phosphorylation of the fructose 1,6 biphosphatase enzyme done
It’s phosphorylated when glucose is low so that gluconeogensis happens to make more glucose
Phopshoprotien phosphatase add the phosphate group to the serine residue of pfk 2 domain
Also The glucagon hormone stimulates phosphokinase A to turn on fructose bisphosphatase 2.
This makes fructose 1,6 bisphosphate turn into fructose 6 phosphate and make gluconeogensis happen.
High glucose =
Low glucose =
More glycolysis less gluconeogeneis
Opposite
Where does gluconeogeneis happen
In the livet
How much
Adp
GDP
Nad+
Made in gluconeogensis
What is the delta g
4
2
2
-38
How much
Atp
Nadh
Pyruvate
Made in glycolysis
What is the delta g
2
2
2
-90
Why is gluconeogensis more energetically favourable
It uses. 6 higher energy bonds to make glucose
(4atp and 2 gtp)
