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
does insulin normally stimulate the breakdown or storate or tings
storage
what two hormone regulators of glucogenogenenis are also seen in glycogenolysis and glycogeneis
glucagon and insulin
insulin is an inhibiot or gluconeogensis AND…
glycogenolysis (promotes glycogenesis)
glucagon is an actvivator of gluconeogenesis AND
glycogenolysis
what is another pathway that branches off from glycolysis
pentose phosphate pathway
what is the connecting compoiund of glycoglysis =, gluconeogenis and PPP
glucose 6 phospate
what is the end porducts of the PPP
ribose
NADPH
what type of raection is the PPP
oxidative.reduction
what is one of the main functions of the PPP
elimination of free radicals
what 3 componets does PPP generate
1) NADPH reducing agents
2) ribose 5P
3) glycolysis intermiediations through reversible reactions
how does glucose end up as ribose
Donates its electrons and hydorgens to NADP+ which gets reduced to NADPH adn then changes to a form of ribose
what type of reactions is NADPH important for
ANABOLIC REACTIONS
what are 3 examples of the functions of NADPH
1) fatty acid synthesis
2) glutathione reduction (important for antioxidant)
3) detoxfications
why is generating a ribose 5 phospahte important in PPP
because it is a precursor for synthesis of nucleotide biosynthesis
do the intermediates of PPP get wasted
no , they are able to enter glycolysis to make atp by reversible reactions
what is the main difference between NADH and NADPH
There is a negatively charged phoshpate group added on to the ribose sugar for NADP
