Gluconeogenesis Flashcards
Gluconeogenesis is the
synthesis of glucose from non-carb precursors
- important for fasting/starvation
- liver and kidney help to main the glucose in the blood
What are the precursors for gluconeogenesis?
1) Lactate (from skeletal muscle via lactic acid fermentation)
2) Amino acids (from proteins in diet vs starvation = breakdown of proteins in skeletal muscle)
3) Glycerol from triacylglycerols hydrolysis (may enter gluconeogenic or glucolytic pathway at DHAP)
Pyruvate to phosphoenolpyruvate
Pyruvate + ATP + CO2 +H2O -> oxaloacetate +ADP + Pi + H+
enzyme: pyruvate carboxylase
Oxaloacetate +GTP -> phosphoenolpyruvate + GDP + CO2
enzyme: phosphoenolpyruvate carboxykinase
Pyruvate to oxaloacetate requires:
Biotin (vit B7) - carrier of activated CO2, occurs in the mitochondria
Need to get oxaloacetate from mitochondria to cytosol!!
Oxaloactate -> malate (which now passes through membrane to cytosol) -> oxaloacetate now in cytosol!
Gluconeogenesis is the same as glycolysis from _____ to ______
Phosphoenolpyruvate to F-1,6-BP
F-1,6-BP to F-6-P enzyme is:
fructose 1,6-biphosphatase
F-6-P to G-6-P is
like in glycolysis
G-6-P to glucose enzyme:
glucose 6-phosphatase
In most tissues, gluconeogenesis ends with the formation of g-6-p because
there is a lack of glucose-6-phophatase, so instead make glycogen
Gluconeogenesis and glycolysis regulation for f-6-p < > f-1,6-bp
1) energy is needed = high AMP
- glycolysis/PFK is activated by AMP and F-2,6-BP
- PFK is inhibited by citrate, H+, and ATP
2) Energy is high = high ATP and high citrate
- Gluconeogenesis/Fructose 1,6-biphosphatase is activated by citrate
- F-1,6-BP is inhibited by AMP amd F-2,6-BP
In the liver, gluconeogenesis and glycolysis regulation
1) Energy is needed = high ADP
- F-1,6-BP activates pyruvate kinase
- ATP and Alanine inhibit pyruvate kinase
2) Energy is high = high ATP, alanine, and acetyl CoA
- ADP inhibits PEP carboxylase and pruvate carboxylase
- Acetyl CoA actives pyruvate carboxylase
