lecture 8:precursors of gluconeogenesis, cori cycle, hormonal regulation, beginingn of PPP Flashcards
is gluconeogenesis just the reverse of of glycolysis
no
why is gluconeogenesis not the reverse of glycolysis
because there are 3 metabolic pathways that are unidirectional (not revresible)
ex: pyruvate cannot go back to phosphoenolpyruvate since it is unidirectional
why are some reactions reversible in glycolysis
to allow the reaction to move in different directions depending on the amount of substrate present
where does gluconeogenesis occur
in the liver
what is the enzyme taht allows glucose to go back into the circulation from the liver and what is its function
glucose 6 phosphotase
glucose 6 phosphate to lose its phsopate (gives it to enzyme) and become glucose
how many unique reactions are there in gluconeogenesis
4
where do the unique reacitons happen
in the places of glycolysis that are non reversible
what are the 4 unique reactions/enzymes in the liver for gluconeogenesis
glucose 6 phospate > glucose by GLUCOSE 6 PHOSPHOTASE
fructose 1-6 biphosphotate > frcutose 6 phosphate by FRUCTOSE 1-6 BIPHOPSOHOTASE
oxaloacetate > phosphoelolpyruvate by PEP CARBOXYKINASE
pyruvate > oxaloacetae by PYRUVATE CARBOXYLASE
WHat is the first step pyruvate must to to because phosphoemolpyruvate
must turn into oxaloacetate by pyruvate carboxylase first
what happens to oxaloacetate
goes to phosphoenolpyruvate by PEP carboxykinase
true or false: all the precursors enter gluconeogenesis at the same time
false
explain glycerol entering the gluconeogenesis pathway
glycerol (broken from fatty acid) enters liver and can be phosphorylated
> it can go to glycerol 3 phosphate (gets energy)
> it then has enough energy to enter and go through the glucogenogenitic pathweay and eventually become glucose
explain alanine entering the gluconeogenic pathway
Alanine coming from a protein can easily be changed into pyruvate by losing a nitrogen group
ALANINE AMINO TRANSFERASE will change it to pyruvate and then continue the pathway as normal
explain lactate (glycolitic end product) entering the gluconeogetic pathway
Lactate can easily go to pyruvate by the enzyme lactate dehydrogenase
true or false: lactate and alanine enter the gluconegenesis process at the same place
true, both turn into tpyurvate by different enzymes
when is the cori cycle used
during high intensity exercise (or recovered) cellular hypoxia (altitude)
why does cori cycle use gluconeogenesis
it uses it to bring the cells back down to homeogenesis
ex: eleminate high levels of lactic acid in the blood stream
explain the cori cycle
When lactate exits the skeletal muscle and into the circulation, there will be an increase in lactic acid
To prevent lactic acidosis, the lactate will be taken up by the liver and be transfered into glucose so the cycle continues
what is the energy cost for gluconeogenesis
6 atp
what are the 3 main hormones that regulate gluconeogenesis
+ glucagon
+glucocorticords (cortisol)
- Insulin
where is cortisol formed
adrenal medulla, in the cortex
where are the two stimulators of gluconeogenesis
cortisol
glucagon
what is the inhibiot of gluconeogeneis
insulin
Does glucagon normally stimulate the break down or build up of things
breaking down/using things
