Hi, during prolonged fasting gluconeogensis is upregulated whereas glycolysis is downregulated. Why would glycolysis be down regulated during a prolonged fasting state if the body is in need of energy during this time?
Metabolism during prolonged fasting
- Thread starter malikhind
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There is not enough plasma glucose to perform glycolysis, therefore the body has to find other ways to make it (eg gluconeogenesis)
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Glycolysis and gluconeogenesis are essentially opposites: one breaks down glucose while the other creates glucose. Further, glycolysis is upregulated when there are high blood glucose levels (hyperglycemia), while gluconeogenesis is upregulated when there are low blood glucose levels (hypoglycemia). So, logically, you can see how it wouldn't make much sense to upregulate both of these metabolic pathways concurrently.
Glycolysis and gluconeogenesis are reciprocally regulated. Low glucose, glucagon, GProtein cascade, adenylate cyclase makes cAMP from ATP, activates pka, bifunctional enzyme phosphorylated, F-2,6-bisphosphatase active which breaks down f26bp which inhibits pfk1 (glycolysis enzyme). High glucose ppp1 de phosphorylates the bifunctional enzyme and a kinase makes makes f26bp from f1p which stimulates pfk1 (glycolysis)
