Gluconeogenesis Flashcards
Process of synthesizing glucose from non-carbohydrate precursors in order to PREVENT HYPOGLYCEMIA during a fast
Gluconeogenesis
Site of Gluconeogenesis
Liver (90%)
Kidney (10%)
occurs in BOTH MITOCHONDRIA and CYTOSOL
Substrates for Gluconeogenesis
Intermediates of Glycolysis through the Cori Cycle
Glycerol and Propionyl CoA from triacyglycerols
Carbon skeletons of Glucogenic Amino Acids
Product of Gluconeogenesis
Glucose
Rate Limiting Step of Gluconeogenesis
Fructose 1,6 bisphosphate –> Fructose 6-phosphate
FRUCTOSE 1,6 - BISPHOPHATASE
(-) by fructose 2,6 BP
Irreversible Enzymes
PYRUVATE CARBOXYLASE (mitochondria)
pyruvate –> OAA
requires biotin, ATP
activated by acetyl CoA
PHOSPHOENOLPYRUVATE CARBOXYKINASE (cytosol)
OAA –> PEP
requires GTP
FRUCTOSE 1,6 BISPHOSPHATASE (cytosol) fructose 1,6-BP --> fructose 6 phosphate citrate (+) AMP (-) fructose 2,6 BP (-)
GLUCOSE 6 PHOSPHATE (ER)
G6P –> glucose
Lactate formed by glycolysis in skeletal muscle is transported to the liver where it is converted back to glucose through gluconeogenesis
lactate –> glucose
Cori Cycle
Gluconeogenesis from pyruvate requires
Cleavage of 6 HIGH ENERGY PHOSPHATE bonds
Oxidation of 2 NADH
Energy is derived from the OXIDATION OF FATTY ACIDS
In hyperglycemia, the glomerular filtrate may contain more glucose that can be reabsorbed
Occurs when the venous blood glucose concentration exceeds 10.0 mm0l/L (renal threshold)
GLUCOSURIA
Excessive gluconeogenesis in response to injury and infection
Associated w/ poor outcome
Hyperglycemia in critically ill patients
High fetal glucose consumption
Risk of maternal and fetal hypoglycemia especially during fasting
Hypoglycemia during pregnancy
Enzymes of gluconeogenesis are not yet fully developed
Premature and low birth weight infants more susceptible because they have little adipose tissue
Hypoglycemia in neonates
Amino acid increased in blood during starvation
Alanine
