Energy Storage- Glucogen And Fat Flashcards
How is glycogen stored?
Glycogen is stored as granules
Describe glycogen’s structure.
A polymer consisting of chains of glucose residues. These residues are linked by a-1-4 glycosidic bonds with a-1-6 glycosidic bonds forming branch points every 8-10 residues.
What is the glycogen store function in the liver?
G6P converted to glucose and exported to blood. Liver glycogen is a buffer of blood glucose levels.
What is the glycogen store function in muscle?
Muscle lacks the enzyme glucose-6-phosphotase. G6P enters glycolysis for energy production.
What’s the rate limiting enzyme in glycogen synthesis and glycogen degradation?
GS: Glycogen synthase. GD: Glycogen phosphorylase
Examples of glycogen storage diseases.
von Gierke’s disease: glucose-6-phosphatase deficiency. McArdle disease: muscle glycogen phosphorylase deficiency.
Describe gluconeogenesis
The production of new glucose which occurs in liver and to a lesser extent in kidney cortex. It has three major precursors: lactate, glycerol, amino acids.
What are the key enzymes in gluconeogenesis?
Phosphoenolpyruvate carboxyinase catalyses GTP-> GDP. Fructose 1,6-bisphosphatase catalayses F 1,6-BP -> F6-P. Glucose-6-phosphatase catalyses G6P -> Glucose
Regulation of gluconeogenesis.
Glucagon stimulates (increases the enzyme amount), insulin inhibits (decreases enzyme amount).
Describe storage and utilisation of lipids.
Triacylglycerols are hydrophobic and therefore are stored in an anhydrous form in adipose tissue. They are utilised in prolonged exercise, stress, starvation and during pregnancy.
Describe fatty acid synthesis
Mainly occurs in liver. Glucose -> pyruvate in the cytoplasm, pyruvate enters mitochondria and forms acetyl-CoA & OAA which condenses to form citrate. Citrate is cleaved back to acetyl-CoA and OAA in cytoplasm. Acetyl-CoA carboxylase produces malonyl-CoA from A-CoA. Fatty acid synthase complex builds fatty acids by addition of 2 carbon units.
What is the glycogen store function in the liver?
Phosphorylation and activation of HSL. Insulin leads to de-phosphorylation and inhibition of HSL.
