Glycogen Flashcards
How many reducing ends does glycogen have?
1
Where is glycogen cleaved?
Non-reducing ends
What two types of bonds does glycogen have? Which is branching?
Alpha 1,4 and Alpha 1,6 (branch)
What are the three benefits to storing energy in glycogen?
Can be rapidly mobilized, can be used under anaerobic conditions, and can convert to glucose to maintain blood homeostasis
Where is the majority of glycogen stored?
Liver and muscle
What is the shape of glycogen?
Granules (highly branched)
Where are glycogen synthesis/degredation taking place?
Cytosol
Follow the degradation of glycogen
Glycogen to glucose-1-P via debracnhing enzyme and glycogen phosphorylase. G1P to G6P via phsophoglucomutase. G6P to glucose via glucose-6-phosphatase (liver only)
Glycogen linear chains are broken down to what?
Glucose 1-P via glycogen phosphorylase
What is phosphorylytic cleavage? Where does it happen in glycogen degredation?
Glycogen to G1P, uses phosphorus instead of water to cleave a bond
Describe the function of the branching enzyme
When linear chain is down to 4 glucose molecules, 3 are removed and added to the longer chain and 1 free glucose molecule is released.
T or F: For every 8 glucose molecules in glycogen taken to G1P, 1 free glucose molecule is released
T
What is the function of phosphoglucomutase?
G6P to G1P
T or F: Glycogen degredation is the same in liver as it is in muscle
T
Gylcogen is synthesized by taking G1P to?
UDP glucose via UDP glucose pyrophosphorylase
UDP Glucose requires what energy?
2 ATP, release of pyrophosphate pulls the reaction toward products
T or F: G6P and G1P are interchangeable
T via phosphoglucomutase
What is the core protein at glycogen synthesis?
Glycogenin
What residue is the beginning of glycogen on a glycogenin protein?
Tyrosine. The OH is super important for esterification
How is UDP-glucose made into glycogen?
Via glycogen synthase which puts glucose on the chain and removes UDP
What forms branches in glycogen? What are the requirements?
Branching enzyme, need at least 4 residues between each branch point (takes glucose chains from the end of a linear branch and adds on to glycogen granule)
In glycogen formation, the anomeric carbon is attached to?
Glycogenin
What happens to glycogen when cAMP cascade is activated?
PKA is activated which P glycogen inactivating it, and Ps Glycogen phosphorylase kinases which then Ps glycogen phosphorylase to activate degredation
Describe low blood sugar effect on glycogen in liver
Low Blood glucose release glucagon insulin goes down then cAMP activated which causes PKA to inactivate glycogen synthetase (Ps it) and Ps glycogen phosphorylase kinase which Ps glycogen phosphorylase activating glycogen degredation
What is the purpose of glycogen phosphorylase kinase?
To activate a bunch of glycogen phosphorylase, makes it very rapid versus a 1:1 activation by PKA
What is the regulator of Glycogen synthesis? Degredation?
Glycogen synthetase; Glycogen phosphorylase
What happens to glycogen in the liver in the presence of insulin?
cAMP is deactivated, Glycogen synthetase is dephosphorylated and activated whereas GPK and glycogen phosphorylase are dephosphorylated and made inactive
Where does the liver get ATP from?
Typically from adipose
Where does the energy for gluconeogenesis in the liver come from?
Fat
How does fat provide energy to liver?
FA and glycerol are brought to liver and broken into acetyl CoA for energy synthesis
Free glucose can be released from liver and generally not from the muscle, why?
Liver has glucose-6-phosphatase and muscle does not (releases one per debranching enzyme potentially however)
Ephinephrine on muscle does what in regards to glycogen?
Activates cAMP cascade and so on to activate glycogen phosphorylase and inactivate glycogen synthetase
What binds to liver in order to tell liver to release glucose via gluconeogenesis?
Ephinephrine and glucagon
T or F: Epinephrine is stronger than insulin and can overwhelm glycogen synthesis when competing
T; think fight or flight
P glycogen synthetase is?
Inactive (in liver and muscle)
P glycogen phosphorylase is?
Active (in liver and muscle)
What regulates glycogen synthetase?
Positive: Glucose 6-P
Negative: phoshphorylation
What regulates Glycogen phosphorylase?
Negative: ATP, Glucose 6 P, Glucose in liver
Positive: AMP in muscle, phosphorylation
T or F: GLUT-4 is in the liver
F; it is only in muscle insulin dependent
Insulin is a universal signal for?
Energy storage (glycogen or as fatty acid)
Glycolysis happens in the liver primarily for?
FA synthesis
Von Gierke Disease is?
Mutation in G6Phosphatase leading to hypoglycemia and enlargement of the liver
Pompe disease is?
Alpha 1,4 glucosidase lysosomal disorder leading to heart failure
What is Cori disease?
debranching enzyme is defective leading to Von Gierke type symptoms but less severe
What is Andersen disease?
Branching enzyme is defective leading to cirrhosis of liver and early death
What is McArdle diesease?
Phosphorylase is defective leading to muscles not getting energy and not functioning under strain. Only in muscle
What is Hers disease?
Phosphorylase is defective in liver leading to inability to break down glycogen (does not affect gluconeogenesis)
