Where in the Liver is glycogen stored?
In the cytoplasmic granules containing most of enzymes required for synthesis and degradation
How many enzymes are used in the removal of branches during glycogenolysis?
there are 2:
Glucotransferase and glucosidase
Debranching enzyme, transfers the 3 of the 4 remaining glucoses to another branch after the glucose was cleaved
In glycogenolysis: When 3 of the 4 remaining glucose are debranched, what happens to them?
Glucotransferase enzyme is the one that removes them and then it transfers it to the nonreducing end of another chain
What happens to the single residue that is broken off from the glycogen?
The single residue is called Glucose 1-Phosphate. The Glu 1-P turns into Glucose 1,6-Phosphate, and then to Glucose 6-Phosphate
breaks down glycogen (n) and Pi into glycogen (n-1) and glucose-1 phosphate - cleaves at the alpha (1-4) bonds. Cannot break alpha (1-6) bonds
What is the pathway to go to Gluc-6-P? Name the enzymes also.
From Glycogen→ (glycogen phosphorylase, glucotransferase, and glucosidase) → Glu-1-P → (Phosphoglucomutase) → Glu-1,6-P → (Phosphoglucomutase)
An enzyme that transfers a phosphate group on a glucose monomer from the 1' to the 6' position in the forward direction or the 6' to the 1' position in the reverse direction.
To be specific, it facilitates the interconversion of Glucose 1-phosphate and Glucose 6-phosphate.
Glycogen in the liver and muscle.. Explain
Glucose-1-phosphate is converted to G6P - in muscle this enters the glycolytic pathway (first reaction is bypassed - Extra ATP), in the liver glucose 6-phosphatase is used to produce free glucose which can leave the liver and enter the bloodstream
Does the Glu-6-P turns into glucose in the muscle? Explain
No. It stays in the muscle. Gluc-6-P turns straight to energy. Glucose stays in muscles
Does Glu-6-P turns to glucose in the Liver? Explain
Yes. glucose 6-phosphatase is used to produce free glucose which can leave the liver and enter the bloodstream
What is the source of glycogen synthesis?
UDP-Glu (activated glucose molecule, it is the source of growing glycogen chain)
UDP-Glu does what
Adds the glucose residues to growing glycogen chain and transfers glucose to protein primer (base).
Pyrophosphatase is equal to ???
hydrolyze same energy as ATP. Same amount in calories and drives the reaction
Catalyzes the following reaction needed for glycogenesis: primer + UDPG → Primer + 1 glucose + UDP
Essentially adds glucose to the growing glycogen chain
Turned on by insulin and removing phosphate group
Turned off by epinepherine and glucagon and by protein kinase (adding phosphate group)
Fragments from alpha (1,4) glucose chain to C6 of another chain, glycogen synthase - branch elongation (glycogen synthesis)
What does glucagon and epinephrine do as regulating hormone for glycogen?
it promotes glycogenolysis:
glucagon → g protein → active adenylyl cyclase → cAMP (+) → activates glycogen phosphorylase kinase b → glycogen phosphorylase kinase a → activates glycogen phosphatase a → glycogen is degraded
What does insulin do as a regulating hormone for glycogen?
It promotes glycogenolysis:
insulin → deactivates glycogen phosphorylase a → glycogen phosphorylase b→ which deactivates glycogen phosphorylase kinase a → glycogen phosphatase kinase b → glycogen
What type of reaction happens when cAMP activates glycogen phosphorylase b to glycogen phosphorylase a?
phosphorylation (adds P)
Where is calcium released from?
it is released when the muscle contracts and comes from the endoplasmic reticulum.
How does calcium promote glycogenolysis?
Once it is released, it binds to calmodulin subunit of phosphorylase kinase and activates glycogen phosphorylase b without phosphorylation.Then it activates glycogen phosphatase.
howHow is gycogenesis regulated?
1. by the addition and removal of phosphate group in glycogen synthase.
2. insulin and glucagon
How is glycogen synthase covalently modified?
by addition and removal of a phosphate group:
Glycogen synthase a and b:
Dephosphorylated (a) active
Phosphorylated (b) inactive
Explain how glucagon down regulates glycogenesis/
Glucagon activates cAMP, activates protein kinase, adds Phosphate to glycogen synthase and it inactivates it to glycogen synthase b (phosphorylated form)
Explain how insulin up regulates glycogenesis
activates glycogen synthase b to glycogen synthase a ( dephosphorylated form)
what down regulates glycogen phosphorylase in the liver?
Glucose-6-P, ATP, and Glucose (means their's a lot of energy in the liver so there's no need to break down glycogen)
Why doesn't glucose down regulates glycogen phosphorylase in the muscle?
because it doesn't have to leave the muscle it turns straight to energy
What up regulates glycogen phosphorylase in the muscle
Calcium and AMP (low energy and contraction of muscle)