gluconeogenesis Flashcards
How much glucose does the brain use each day?
120 grams
How much glucose in the body?
190 grams from glycogen stores, 20 grams circulating in the blood.
In the absence of dietary input, how long does liver glycogen meet demand for?
10-18 hours.
When all glycogen stores are depleted, glucose is formed from what precursors ?
Lactate, pyruvate, glycerol, a-ketoacids.
what is gluceogenesis?
The pathway in which glucose is synthesized.
Around 90% of gluceogenesis occurs where?
The liver, the other ten is in the kidneys.
4 enzyme catalysed reactions are used to circumvent the 3 irreversible reactions of glycolysis.
Bypass 1 - pyruvate kinase = 3 steps
Bypass 2 - phosphofructokinase = 1 step
Bypass 3 - hexokinase = 1 step
name and explain bypass1, step 1.
carboxylation of pyruvate. Where pyruvate becomes oxaloacetate by enzyme pyruvate carboxylase which is only found in mitochondria of liver and kidney.
Explain bypass 1, step 2.
Oxaloacetate is converted to malate in order to cross the inner mitochondrial membrane by enzyme ‘mitochondrial malate dehydrogenase’. Once in the cytosol, malate is re-oxidised to oxaloacetate by ‘cytosolic malate dehydrogenase.
Explain bypass 1, step 3.
Oxaloacetate is decarboxylated and phosphorylated in the cytosol to phosphoenolpyruvate by ‘phosphoenolpyruvate carboxykinase’.
Explain bypass 2.
The dephosphorylation by hydrolysis of fructose-1,6-bisphosphate. catalysed by enzyme fructose bisphosphatase bypasses the irreversible phosphofructokinase reaction.
Explain bypass 3.
