Gluconeogenesis, Glycogenesis, Glycogenolysis

[MedPR]

Ok so gluconeogenesis is the formation of glucose from non-carbohydrate sources.. so stuff like pyruvic acid, lactic acid, and amino acids.

Glycogenesis is the formation of glycogen from glucose..?

Glycogenolysis is the formation of glucose from glycogen?

I understand that glycogenesis and glycogenolysis occur in the liver, but where does gluconeogenesis occur? And which is more important for glucose...Which yields more glucose? Gluconeogenesis or glycogenolysis?

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[chiddler]

Ok so gluconeogenesis is the formation of glucose from non-carbohydrate sources.. so stuff like pyruvic acid, lactic acid, and amino acids.

Glycogenesis is the formation of glycogen from glucose..?

Glycogenolysis is the formation of glucose from glycogen?

I understand that glycogenesis and glycogenolysis occur in the liver, but where does gluconeogenesis occur? And which is more important for glucose...Which yields more glucose? Gluconeogenesis or glycogenolysis?

Gluconeogenesis occurs in the liver, as well.

Which yields more glucose? Odd question. Gluconeogenesis forms one glucose, and glycogen yields as many glucoses as there are glucose monomers. Glycogen is a glucose polymer, right?

 

[MedPR]

Gluconeogenesis occurs in the liver, as well.

Which yields more glucose? Odd question. Gluconeogenesis forms one glucose, and glycogen yields as many glucoses as there are glucose monomers. Glycogen is a glucose polymer, right?

I meant to ask which is more useful for the body.. Like, which one has a greater effect on increasing plasma glucose levels? In other words, if you administered an inhibitor to one of them, which would be more damaging?

 

[chiddler]

I meant to ask which is more useful for the body.. Like, which one has a greater effect on increasing plasma glucose levels? In other words, if you administered an inhibitor to one of them, which would be more damaging?

I don't know that :<

 

[mcloaf]

I meant to ask which is more useful for the body.. Like, which one has a greater effect on increasing plasma glucose levels? In other words, if you administered an inhibitor to one of them, which would be more damaging?

The two have different physiological roles. Glycogenolysis provides glucose/energy over a relatively short (I believe about ten minutes, once creatine phosphate stores are used up) period of time. Muscles will consume their own endogenous glycogen stores for energy while the liver can both consume the glucose produced itself, or export it to the blood stream.

Gluconeogenesis takes place almost exclusively in the liver (a bit in the kidneys), and the glucose produced is exported to the blood stream. Gluconeogenesis only occurs during a prolonged fast when blood glucose is falling.

I imagine glycogenolysis provides a larger spike in blood glucose levels, but I'm not sure which produces more glucose overall. You've got quite a bit of glycogen stored in your body, but it's very hydrated. On the other hand, if you really need to use them you've got quite a bit of glucose precursors.

EDIT: As I read over my answers I see I wasn't clear about a few things (for example, of course you break into your glycogen stores when you're fasting, etc.), but hopefully you get the idea. If not let me know what I can hopefully clear up.

 

[MedPR]

The two have different physiological roles. Glycogenolysis provides glucose/energy over a relatively short (I believe about ten minutes, once creatine phosphate stores are used up) period of time. Muscles will consume their own endogenous glycogen stores for energy while the liver can both consume the glucose produced itself, or export it to the blood stream.

Gluconeogenesis takes place almost exclusively in the liver (a bit in the kidneys), and the glucose produced is exported to the blood stream. Gluconeogenesis only occurs during a prolonged fast when blood glucose is falling.

I imagine glycogenolysis provides a larger spike in blood glucose levels, but I'm not sure which produces more glucose overall. You've got quite a bit of glycogen stored in your body, but it's very hydrated. On the other hand, if you really need to use them you've got quite a bit of glucose precursors.

EDIT: As I read over my answers I see I wasn't clear about a few things (for example, of course you break into your glycogen stores when you're fasting, etc.), but hopefully you get the idea. If not let me know what I can hopefully clear up.

Makes sense, thank you.

EK says that gluconeogenesis is the production of glucose and glycogen. Is that a typo?

From page 107 in the paragraph about Cortisol:

Gluconeogenesis is the creation of glucose and glycogen, mainly in the liver, from amino acids, glycerol, and/or lactic acid.

Does gluconeogenesis produce glucose and then once it meets a quota or satisfactory amount, start producing glycogen instead for storage?

 

[mcloaf]

I believe that has to be a mistake. Their logic would be that because gluconeogenesis produces glucose, and glycogen is made of glucose, some of the glucose from gluconeogenesis could be used for glycogenesis.

The easiest way to see why this doesn't make any sense is to look at the energy situation of someone performing gluconeogenesis. As I said before, this is only going to be occurring when you've run out of more readily available stores of energy, as reproducing glucose in your liver from glycolytic intermediates is not energetically favorable and is going to require an input of cellular energy (it will vary depending on what compound you start from). Any of the hard-won glucose your liver is producing is going to be exported to the blood stream and used by your brain and tissues, not stored as glycogen. You store glycogen when you have enough glucose around that you can afford to save some for leaner times.

 

[MedPR]

I believe that has to be a mistake. Their logic would be that because gluconeogenesis produces glucose, and glycogen is made of glucose, some of the glucose from gluconeogenesis could be used for glycogenesis.

The easiest way to see why this doesn't make any sense is to look at the energy situation of someone performing gluconeogenesis. As I said before, this is only going to be occurring when you've run out of more readily available stores of energy, as reproducing glucose in your liver from glycolytic intermediates is not energetically favorable and is going to require an input of cellular energy (it will vary depending on what compound you start from). Any of the hard-won glucose your liver is producing is going to be exported to the blood stream and used by your brain and tissues, not stored as glycogen. You store glycogen when you have enough glucose around that you can afford to save some for leaner times.

Makes sense, thank you.