FCELL- carbohydrate metabolsim Flashcards
where does glycogen synthesis and degradation take place
in the liver and muscle
where, when and why does glycogenesis take palce
takes place in the liver and skeletal muscle
takes place when blood glucose levels are high
glycogen is a safe way to store glucose
what is glycogenesis regulated by
insulin
how is glycogen formed
from linking glucose molecules by alpha 1-4 and a1-6 glycosidic bonds
formed on a protein known as glycogenin
regulated by glycogen synthase
outline the process of glycogen synthesis
G6P (phosphoglucomutase
G1P (UTP uridine triphosphate)
UDP-glucose + glycogenin
builds up chain (glycogen synthase) - alpha 1,4
forms branches (branching enzyme) alpha 1,6
why use glycogen as a storage molecule
cannot store glucose as it is osmotically active
the branched structure means it can be metabolised quickly
where does glycogenolysis occur and why
occurs in liver and muscles when glucose levels are low
what is glycogenolysis stimulated by
glucagon, adrenaline, noradrenaline and growth hormone
outline the breakdown of glycogen
phosphorylase breaks the alpha 1,4, bonds
produces glucose 1 phosphate which is converted to glucose 6 phosphate by phosphoglucomutase
breaks down alpha 1-6 links by debranching enzyme
puts 4 residues onto end of chain (transferase)
outline where glycogen phosphorylase has a role and what it is regulated by
role in glycogenolysis
regulated by allosteric interactions that signal the energy state of the cell
regulated by reversible phosphorylation regulated by hormones such as insulin, glucagon, adrenaline and noradrenaline
what is the active vs inactive form of glycogen phosphorylase
active - phosphorylase a
inactive phosphorylase b
what is gluconeogenesis
synthesis of glucose from non-carbohydrate sources - triglycerides, lactate, amino acids
where does gluconeogenesis take place and why
takes place in the liver, kidney and a small amount in the small intestine
takes place when the blood glucose levels are low (fasting / starvation)
