Final: gluconeogenesis Flashcards
why is gluconeogenesis important?
helps the body maintain glucose levels during fasting
what does gluconeogenesis use to make glucose? (substrates)
amino acids, lactate, and glycerol
where does gluconeogenesis occur?
mainly the liver (could also be epithelial cells in kidney or intestine
Fasting, where do we get glucose?
1) glycogen stores (12-24 hours) until we run out
2) gluconeogenesis (kicks in 12 hrs in as main provider of glucose)
gluconeogenesis
uses ATP to turn pyruvate into glucose
sources of pyruvate for gluconeogenesis (1)
lactate (lactate dehydrogenase takes Hydrogen from lactate and makes it pyruvate while making NADH)
sources of pyruvate for gluconeogenesis (2)
amino acids (alanine) alanine comes from breakdown of protein and skeletal muscle cells alanine transaminase (vitamin B6 as a cofactor) removes amino from alanine and turns it to pyruvate
during fasting,
pancreas senses low glucose, releases glucagon
there is also low insulin, high epinephrine
gluconeogenesis step 1C
oxaloacetate to phosphoenolpyruvate
enzyme: PEPCK removes a carbon and adds a phosphate
requires GTP
PEPCK regulation
stress hormones: glucagon, epinephrine, and cortisol enhance PEPCK by induction
using glycerol
- glycerol can make DHAP
- glycerol kinase adds phosphate from ATP to C3 on glycerol
- makes glycerol-3-phosphate (G3P)
- glycerol-3-phosphate dehydrogenase converts G3P to DHAP
rate limiting step of gluconeogenesis
fructose-1,6-bisphoshatase
gluconeogenesis 3rd roadblock
PFK1 rxn
in gluconeogenesis, fructose 1,6 bisphosphatase removes phosphate from C1 of fructose-1,6-bisphosphate making fructose-6-phosphate
up-regulation of gluconeogenesis
when liver burns a lot of fat making a lot of ATP
high ATP = enhances fructose-1,6-bisphosphatase
fructose-1,6-bisphosphatase regulation
glucagon activates, insulin inhibits
