Carbohydrate Metabolism Glycogen and Gluconeogenesis Flashcards
(29 cards)
Glycogenesis
synthesis of glycogen from glucose monomers
Glycogenolysis
breakdown of glycogen to form glucose monomers
what is glycogen
main storage form of glucose in liver and muscle cells
what types of links make straight chains and branches in glycogen
how is glycogen packaged within cells
straight chains - alpha 1-4 glycosidic links
branches - alpha 1-6 glycosidic links
packaged in granules
how many glucose residues make up a glycogen primer
at least 4
what protein attaches to a glycogen primer
glycogenin
when making glycogen, what is made to prevent glucose-6-phosphate from entering glycolysis
what enzyme does this
glucose-1-phosphate
phosphoglucomutase
what is UDP-glucose
an activated form of glucose (activated intermediate)
what is the difference between liver glycogen and muscle glycogen roles
depends on the enzymes present in either tissue
liver - broken down between meals and released into the blood to maintain blood glucose levels
muscle - not able to be released into the blood, broken down to provide energy for that muscle cell during short bursts
glucose-1-phosphate -> UDP-glucose enzyme
side product
UDP-glucose pyrophosphorylase
pyrophosphate ion
UDP-glucose -> glycogen enzyme
side product
glycogen synthase
UDP
where is energy stored in nucleotides
the phosphate ester linkage
what happens to pyrophosphate when it is released
why is this important
it is hydrolysed by pyrophosphatase to 2 inorganic phosphate
drives the reaction in the forward direction towards UDP-glucose synthesis
what is the rate-limiting enzyme of glycogenesis
glycogen synthase
which enzyme extends existing branches of glycogen
which enzyme introduces branches to glycogen
glycogen synthase
transglycosylase
how often does transglycosylase introduce alpha 1-6 glycosidic branches to glycogen
approx. every 10 glucose residues
what hormone acts when blood glucose is higher than normal
what cells secrete it
insulin
pancreatic beta cells
what hormone acts when blood glucose is lower than normal
what cells secrete it
glucagon
pancreatic alpha cells
glycogen -> glucose-1-phosphate enzyme
glycogen phosphorylase
what is the rate-limiting enzyme of glycogenolysis
glycogen phosphorylase
why does glycogenolysis require an inorganic phosphate
glycogen phosphorylase uses Pi to make glucose-1-phosphate
why can liver glucose-6-phosphate be made into glucose and released into the bloodstream but muscle glucose-6-phosphate cannot
in the liver, different enzymes are present so it can be dephosphorylated
what is gluconeogenesis
synthesis of glucose within the body from non-carbohydrate precursors
what are the precursors to glucose in gluconeogenesis
lactate
amino acids
glycerol
