Glycogen synthesis Flashcards
Where can carbohydrates be stored?
Can be stored as glycogen in the liver and muscles
What happens to excess carbohydrates when glycogen reserves are full?
full excess carbohydrate is converted to fat for storage.
What is Surplus glucose stored as?
It is stored as glycogen
How does Glycogenesis begin?
Begins with the the phosphorylation of glucose by glucokinase and by hexokinase .
How do we activate our glucose molecule
- Glucose is phosphorylated by glucokinase and by hexokinase (this costs 1ATP)
- Then glucose-6-phosphate is converted into glucose-1-phosphate by phosphoglucomutase
- glucose-1- phosphate is converted to uridine diphosphate (UDP) glucose catalysed by UDP glucose pyrophosphorylase
What do glucokinase and hexokinase do?
Phosphorylates glucose into Glucose 6-phosphate (this requires 1ATP)
What does phosphoglucomutase do?
Converts Glucose 6-phosphate into Glucose 1-phosphate
What does UDP- Glucose
pyrophosphorylase do?
Converts Glucose 1-phosphate into UDP glucose
Why does glucose need to be activated before glycogen synthesis can begin?
Glucose needs to be activated before it can be added to the no reducing end of the glycogen chain
How may ATPs does it take to activate glucose?
1
What drives the activation of glucose reaction?
The formation of UDP and pyrophosphate
These pyrophosphate can be phosphorylated to release 2 free energy inorganic phosphates
After guise has been activated what does it need to do?
It needs to be coupled onto our glycogen
What do we need to be able to couple our activated glucose onto glycogen?
A primer
Name the primer we use to couple our activated glucose onto glycogen?
It is glycogen with a minimum number of sub units
How is our initial glycogen formed by?
By glycogenin
Name theentyme that joins glycogen and the active form of glucose
Glycogen synthase
Name the only link glycogen synthase can produce
Glycogen 1,4 linkage
Name a common intermediate found in carbohydrate condensation reactions
Nucleoside diphosphate
What provides the energy needed to link the active glucose to the non reducing end on glycogen ?
The high energy bond between
the sugar and the nucleoside diphosphate
provides the energy needed to link the new
sugar to the non reducing end.
How is the branching of the glycogen completed?
It is completed by transferring a minimum of 6 alpha (1-4) glucan units from the elongated chain onto the sam for neighbouring chain by introducing an alpha (1-6^) linkage
Name the enzyme that helps for branches on glycogen
The branching enzyme
How Does the branching enzyme work?
Works by taking a block of units from the non reducing terminal of a glycogen polymer
It breaks an alpha 1-4 linkage and for an alpha 1-6 linkage
What conditions need to be fulfilled so that the branching enzyme can work?
- You need a minimum chain length of 10-11 sub units
2. Branching enzymes needs to attach at least 4 units into the glycogen chain
What is Andersons disease caused by?
A deficiency in the branching enzyme
What are the consequences of having Andersons disease
Liver failure and death in the first year of life
Talk through the hormonal control of glycogen synthesis
- Insulin receptor (Tyrosine kinase) activated protein kinase
- Protein kinase activates Phosphoprotein phosphatase 1
- Phosphoprotein phosphatase 1 does 2 things:
A. Inhibits glycogen phosphorylase b thus switching go glycogen breakdown
B. Activantes glycogen synthase a so that glycogen synthase occurs
Where is insulin secreted from?
Secreted from the pancreas
When is insulin secreted?
Secreted in response to increased blood glucose
After being secreted from the pancreas where does insulin go?
Insulin travels to taget tissues eg muscles, liver and adipose
There is binds to the membrane receptors and effects metabolise to promote synthesis of glycogen
What does insulin do in the muscle
1 Insulin briefly increases the number of membrane glucose transporters
- Increases glucose uptake from the blood
- Also activates glycogen synthesis so the glucose can be stored as glycogen
What does insulin do in the liver
- Takes up glucose fro blood so insulin doesn’t influence the number of membrane glucose transporters
- Insulin activates glycogen synthesis so liver is able to store more glucose as glycogen
How much glycogen can we sore in the body?
About 300 g
What happens once glycogen stores are full
Glucose entering the liver will be converted into dat and sent to the adipose tissues to be stored
What does insulin do in the adipose tissue
- Insulin briefly increases the number of membrane glucose transporters
- You get an increased glucose uptake fro te blood
- Insulin also stimulates the conversion of guise to fat for storage
What is diabetes type 1
It is insulin dependent diabetes caused by a deficiency of insulin due to beta cell destruction
How I diabetes type 1 treated?
Treated with insulin
What is diabetes type II
It is non insulin dependent diabetes
It is a long term disorder that is primarily characterized by insulin resistance
Give some risk factors of diabetes II?
Obesity
Genetic factors
How is diabetes II treated?
Diet
Exercise
Hypoglycemic drugs,
sometimes insulin.
What oral implications are associated with uncontrolled diabetes?
Elvated blood glucose causes salivary glucose concentration to increase
This has an impact on oral microbiology leading to increased oral disease especially periodontal disease
Name the disease that occurs due to A deficiency in the branching enzyme
Andersons disease
