10/2 Glycolysis & Glycogen Metabolism Flashcards
4 regulatory enzymes of glycolytic pathway
hexokinase/glucokinase
phosphofructokinase-1
pyruvate kinase
pyruvate dehydrogenase
hexokinase
D-glucose —> G6P
requires ATP
(-) G6P
low specificity for glucose
glucokinase
D-glucose —> G6P
requires ATP
(+) insulin
high specificity for glucose
phosphofructokinase-1
F6P ---> F-1,6-B requires ATP (-) ATP, citrate (+) AMP, F-2,6-B Allosteric
fructose-2,6-bisphostphate
levels lowered by glucagon/cAMP
inhibits glycolysis
activates gluconeogenesis
pyruvate kinase
phosphoenol-pyruvate —> pyruvate
requires ADP
(-) ATP, F-1,6-B, phosphorylation by glucagon/PKA
liver only
pyruvate dehydrogenase
pyruvate --> acetyl-CoA requires NAD+ regulated by rate of ATP utilization (-) NADH, Acetyl-CoA (+) ADP, Ca2+
aerobic glycolysis (end product, energy produced, regeneration of NAD+)
pyruvate (can be fully oxidized to CO2)
2 ATP per glucose
NAD+ is regenerated by ETC in mitochondria
anaerobic glycolysis (end product, energy produced, regeneration of NAD+)
lactate (from pyruvate and NADH)
2 ATP per glucose
NAD+ is regenerated by lactate formation
glycogenesis
synthesis of glycogen
requires energy from UTP
G1P —> UDP-glucose
regulated enxyme: glycogen synthase (phosphorylated = inactive), adds glucosyl residue from UDP-glucose to chain but needs primer glycogenin
glycogenolysis
breakdown of glycogen
muscles and liver
glycogenolysis in the muscles
G6P for energy via glycolysis
(+) epinepherine
regulated enzyme: glycogen phosphorylase (active when phosphorylated), cleaves glycosyl residues to release G1P
glycogenolysis in the liver
G6P for hydrolysis to glucose to maintain blood [glucose] (by G6Pase)
(+) epinepherine, glucagon
regulated enzyme: glycogen phosphorylase (active when phosphorylated), cleaves glycosyl residues to release G1P
