Metabolic pathways- biochem Flashcards
What is glycogenesis?
synthesis of glycogen from glucose
What is glycogenolysis?
breakdown of glycogen to form glucose
What is glucogenesis?
synthesis of glucose from metabolic precursors
Where is glycogen stored?
liver or muscles
When is liver glycogen used?
it is broken down between meals and released to maintain blood glucose levels for red blood cells and the brain
When is muscle glycogen used?
during bursts of physical activity, it provides energy via glycolysis and the TCA
What do glucose levels depend on?
Dietary, glycogenolysis and glucogenesis
what is the structure of glycogen?
it is a polymer of glucose molecules joined by alpha 1-4 glycosidic links, branches are introduced by alpha 1-6 glycosidic links
What is the protein attached covalently to the glycogen primer called?
glycogenin
How are glucose residues added to glycogen?
They must be added to a pre existing glycogen chain that has at least 4 glucose molecules (glycogen primer)
How is glycogen synthesised?
Glucose is phosphorylated by hexikinase into glucose-6-phosphate, this then becomes glucose-1-phosphate due to phosphoglucomutase, glucose-1-phosphate then becomes UDP-glucose due to UDP phosphorylase and then glucose syhnthase turns it into [glucoes] n+1 , ready to be added on to a pre existing glycogen chain
What enzyme introduces the alpha 1-6 glycosidic branches?
transglycosylase
What happens during glycogenolysis?
Glycogen is broken down in to glucose-1- phosphate due to glycogen phosphorylase, glucose-1-phosphate becomes glucose-6-phosphate due to phosphoglucomutase, in skeletal muscle this is used for glycolysis/TCA cycle whereas in the liver it is broken down further into glucose due to the glucose- 6- phosphatase enzyme and this is released into the blood through the GLUT 2 transporters
