gluconeogenesis Flashcards
what can the precursors of gluconeogenesis be?
lactate
AA
glycerol - from triglycerides
glycolysis is usually irreversable. why can gluconeogenesis occur?
the liver has a set of enzymes that bypass the non-reversible reactions of glycolysis
what enzymes are involved in the conversion of pyruvate to PEP?
pyruvate carboxylase and PEP carboxylase
what is the energy input needed to convert pyruvate to PEP?
2 ATP equivalents
where does the pyruvate carboxylase reaction occur?
in the mitochondria
what does the pyruvate carboxylase enzyme do? what does it use to do so and what are the products? are there cofactors?
uses ATP to attach CO2 to pyruvate
requires biotin as a cofactor
acetyl-coA is required to activate enzyme
what does PEP carboxykinase do? what does it use to do so?
uses GTP to phosphorylate decarboxylate axaloacetate in process of converting pyruvate to PEP
where does the PEP carboxylase reaction occur?
in the cytoplasm
is the PEP carboxylase reaction reversible?
no
what does malate dehydrogenase do? why is this necessary?
convert oxaloacetate to malate so that the sugar may enter the mitochondria, where it’s then converted to oxaloacetate again whe out of the mitochondria
necessary for gluconeogenesis because part of reaction (pyruvate carboxylase part) takes place in mitochondria, while the next step (PEP carboxylase) takes place in the cytoplasm but oxaloacetate can’t cross the mitochondrial membrane
what enzymes does gluconeogenesis use?
the reversible enzymes of glycolysis in the reverse direction
fructose-1,6-bisphosphate
G-6-phosphatase
what does fructose-1,6-bisphosphate do?
converts fructose-1,6-bisphosphate to F-6-P
what regulates fructose-1,6-bisphosphate?
citrate and APT activate
F-2,6-bisphosphate and ADP inhibit
what does G-6-phosphatase do? why is this enzyme necessary?
in gluconeogenesis
coverts G-6-P to glucose
necessary because hexokinase and glucokinase are not reversible
what are the steps of the cori cycle? why is it necessary
lactate converted to glucose in the liver
glucose converted to lactate in muscle
necessary so that lactate is converted to glucose so the brain can use it
where does glycerol come from?
the lipolysis of TG
what are the energy requirements of gluconeogenesis from glycerol?
ATP
what does pyruvate dehydrogenase (PDH) do?
usually converts pyruvate to Acetyl CoA but can also convert lactate to oxaloacetate
what are the three enzymes that make up PDH?
pyruvate decarboxylase
dihydrolipyltransacetylase
dihydrolipoyl dehydrogenase
what are the cofactors that PDH uses?
NAD+ Thiamine pyrophosphate (TPP) Lipoic acid FAD coenzyme A
what can the precursors of gluconeogenesis be?
lactate
AA
glycerol - from triglycerides
glycolysis is usually irreversable. why can gluconeogenesis occur?
the liver has a set of enzymes that bypass the non-reversible reactions of glycolysis
what enzymes are involved in the conversion of pyruvate to PEP?
pyruvate carboxylase and PEP carboxylase
what is the energy input needed to convert pyruvate to PEP?
2 ATP equivalents
