Gluconeogenesis Synthesis of glucose from non carbohydrates precursors

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#1

Gluconeogenesis

Synthesis of glucose from non carbohydrates precursors

Precursors/ substrates includes

  1. Lactate
  2. Glycerol
  3. Propionyl coA
  4. Glucogenic amino acids

Not exactly reversal of glycolysis
3 irreversible steps in glycolysis reversed by 4 important enzymes

  1. Pyruvate carboxylase
  2. Phosphoenolpyruvate carboxykinase
  3. Fructose 1,6 bisphosphatase
  4. Glucose 6 phosphatase

Gluconeogenesis
Site - cytosol/ mitochondria
Mostly in Liver and to some extent in renal cortex

  1. Important source of glucose during starvation after depletion of glycogen ( after 18 hrs)
  2. Important source of energy for brain and RBCs

Energy utilized - 6 ATP/ glucose synthesis

Regulation

  1. Induction and repression
    Insulin represses pyruvate carboxylase
    Glucagon induces
  2. Covalent modifications
    By phosphorylation and dephosphorylation of enzymes by hormones
    Glucagon phosphorylate enzymes and activates
  3. Allosteric activation
    By acetyl coA
    And inhibition by F2,6 BP