[FMS] NAM - glycogen synthesis and regulation Flashcards
what kind of molecule is glycogen
polysaccharide
how much glycogen is in tissue stores compared to the liver
400g in tissue
100-200 in liver
what kind of osmolarity does glycogen have
low osmolarity
what kind of fuel store is glycogen
medium-term fuel store
what 2 things control the liver
The liver is sensitive to blood glucose concentration under the control of insulin and glucagon
What is role of glycogen in muscle fuel for exercise?
Glycogen in the muscle does not go to glucose when breaking it down unlike in the liver.
Glycogen goes to glucose-6-phosphate which goes into glycolysis for energy for contraction.
What is the physiological significance of glycogen-branched structure?
More points of contact for enzymes to act on.
what are the 4 important parts of glycogens structure
What are the two types of linkages in glycogen?
- alpha-1,4-glycosidic linkage - makes linear chains
- alpha-1,6-glycosidic linkage - makes branched chains
What are 3 features of biosynthetic pathways?
- ATP or UTP or GTP are needed as cofactors (to ‘drive the reactions forward’)
- one or more enzyme reactions will be irreversible, and alternative enzymes are used for the ‘opposite direction’
- enzyme reactions at the beginning or end of the pathway are tightly regulated
how is glycogen synthesised, including enzymes etc
how is glycogen broken down, including enzymes etc
outline the coordinated regulation of synthesis/ breakdown in liver
outline the coordinated regulation of synthesis/ breakdown in muscles
what happens during muscular contraction
- During muscular contraction, calcium ions are released into the sarcoplasmic reticulum.
- Calcium binds the calmodulin domain of glycogen phosphorylase kinase and activates the enzyme
- This in turn activates the phosphorylase and glycogen is degraded providing energy for contracting muscle
What are the controls in prolonged exercise?
- In prolonged exercise, ATP concentrations are reduced and AMP concentrations begin to rise.
- AMP is an allosteric activator of glycogen phosphorylase.
- Glycogen degradation continues without the need for hormonal interaction ATP is an allosteric inhibitor, so that when energy levels are high, glycogen breakdown stops.
what are the 3 glycogen storage diseases?
“Von Gierke’s Very Enlarged Liver due to Glucose-6-Phosphatase”
Pompe’s Poorly Pumps Muscles and Cardiac due to Lysosomal Glycosides”
“McArdle’s Muscles Must Manage (with) Limited Energy due to Glycogen Phosphorylase
whats the function of AMP in glycogen synthesis
allosteric activator of glycogen phosphorylase
How is glycogen synthase regulated?
BY PHOSPHORYLATION (Glycogen synthase is inactivated by phosphorylation)
whats the function of ATP in glycogen synthesis
allosteric inhibitor, so when energy levels are high, glycogen breakdown stops
What is the difference between a phosphatase, phosphorylase and kinase?
phosphatase removes phosphate and phosphorylase hydrolyses and uses inorganic phosphate. And a kinase phosphorylates using the high-energy phosphate compound ATP.
what enzyme breaks a-1,6 glycosidic bonds between glucose units
DEBRANCHING ENZYME via hydrolysis
what enzyme breaks a-1,4 glycosidic bonds between glucose units
glycogen phosphorylase
in the first step of glycogen synthesis, what is the difference between when hexokinase is used, and when glucokinase is used?
hexokinase in all other tissue
glucokinase in liver ONLY
^BECUASE Hexokinase has a low Km so is able to do this reaction in low glucose concentrations, glucokinase has a high Km So glucokinase is used in the liver because it is a store and you don’t want it all to be used up.
what stimulates and inhibits insulin
vs
what stimulates and inhibits glucagon
Insulin stimulates glucose uptake and utilization while inhibiting glucose synthesis and breakdown.
Glucagon stimulates glucose synthesis and breakdown while inhibiting glucose uptake and glycogen synthesis.
Phosphorylation of what enzyme stops glycogen synthesis - glycogen synthase or glycogen synthase kinase?
Glycogen synthase is the enzyme directly involved in glycogen synthesis, and its activity is inhibited when it is phosphorylated by glycogen synthase kinase (GSK).
So, the phosphorylation of glycogen synthase by GSK stops glycogen synthesis.
Glycogen phosphorylase is the enzyme directly involved in glycogen breakdown, and its activity is inhibited when it is phosphorylated by glycogen phosphorylase kinase (GPK).
So, the phosphorylation of glycogen phosphorylase by GPK stops glycogen breakdown.
therefore answer is GLYCOGEN SYNTHASE KINASE
what activates protein kinases?
cAMP
