BIOL 0280 Lecture Notes - Lecture 12: Gluconeogenesis, Pyruvic Acid, Ribose
7 Nov 2016
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Can store as: glycogen/starch/sucrose, pyruvate, ribose 5- phosphate, ec matrix/cell wall polysaccharides. 3/10 reactions of glycolysis are irreversible in vivo (1, 3, 10) The three irreversible reactions of glycolysis are bypassed to synthesize glucose from pyruvate in gluconeogenesis glucose from pyruvate in gluconeogenesis. Use atp and gtp, requires mg+ and k+ Pyruvate is transported to mitochondria: pyruvate --> oxaloacetate. Pyruvate carboxylase is the first regulatory enzyme in these pathways. Acetyl-coa accumulation is an e-rich signal that signals stimulation of production of glucose: the pathway using cytosolic pep carboxykinase predominates in tissues lacking lactate (like liver) Pyruvate --> oxaloacetate in mitochondria --> malate in cytosol --> oxaloacetate + nadh: the pathway using mitochondrial pep carboxykinase predominates in tissues that accumulate lactate (muscle) Avoids having to shuttle nadh reducing equivalents out of mitochondria. Lactate --> pyruvate + nadh --> transported to mitochondria --> oxaloacetate. Can occur in cytosol or mitochondria (then transported to cytosol) Pyruvate --> pep is energetically expensive (unlike glycolysis)
