Glycogen Metabolism Flashcards
Which parts of the body have the most blood glucose demand?
Brain and RBC. They both consume 80% of the 200g of glucose consumed by body per day.
Why is it necessary for our body to keep replenishing blood glucose levels?
- Our blood plasma only has 10g of glucose at once (around 5% of what our body needs)
- Glucose is absorbed from our intestines only 2-3 hours after a carbohydrate meal.
What are the symptoms of hypoglycemia?
- Compromised brain function (confusion and disorientation)
- Coma
Hypoglycemia: 2.5 mmol/dL (45 mg/dL)
How is glycogen stored in the cytosol?
As granules
Why is glycogen preferred over fat for energy breakdown?
- Muscles cannot mobilise fat as effectively as glycogen.
- Fatty acids cannot be metabolised under anaerobic conditions (G-6-P can enter glycolysis to give pyruvate, then lactose)
- Fatty acids cannot be converted back to glucose. (Pyruvate to Acetyl CoA is irreversible)
Which organ stores the mst glycogen per tissue mass?
Liver (10g/100g)
How much glycogen is stored in muscle and in liver?
Muscle: 300- 400g
Liver: 100g
When is muscle and liver glycogen depleted?
Muscle: Muscle contraction
Liver: After 12-18 hours of fasting
Where is the glucose added to the glycogen primer?
To the non reducing end by the alpha-1,4 glycosidic bond.
What is glycogenin?
Glycogenin is a glycoprotein with two polypepetide chains that acts as the glycogen primer.
What is the property of glycogen synthase?
It is a glycosyl transferase
What is the property of the branching enzyme?
- Transglycosylase (alpha 1,6 bond)
- Glucosidase (alpha 1,4 bond)
What are the properties of the debranching enzyme?
Glucosidase (alpha 1,6 bond)
Why can’t muscle glycogen regulate blood glucose level?
Blood lacks G-6-P phosphatase, hence it cannot dephosphorylate G-6-P to give free dlucose to release into the blood.
Which is the regulatory/ rate limiting step of glycogenesis?
Glycogen synthase
