L23 - Lipid Metabolism 3 Flashcards
What 2 ways can glycerol-3-phospahte be made?
1) from glycerol using the enzyme glycerol kinase, using 1 ATP
2) from DHAP using the enzyme glycerol-3-phosphate dehydrogenase, using NADPH
Where does the pathway split for form TAGs and PAGs individually?
The pathways for TAG and PAG synthesis split after phosphatidate
How do you synthesise a TAG from phosphatidate?
To synthesise TAG the phosphate group is removed by a phosphatase enzyme and then another fatty acid is added
Phosphatidate ——> DAG + Pi ——-> TAG
How do you synthesise a PAG from phosphatidate?
To synthesise PAG the phosphatidate reacts with CTP to activate it
It then reacts with a polar compound (choline, ethanolamine, inositol, serine) to form the PAG
Phosphatidate —> CDP-Diacylglycerol —-> Phosphoacylglycerol
What happens when glucose is limited?
- TAG releases FA which are used to provide energy
- Glucose can be released from storage polysaccharides
- Glycerol can be used in gluconeogenesis to synthesise glucose
What happens when glucose is in excess?
- it is used for energy
- excess converted to fatty acids then TAG
- NADPH and glycerol needed are derived from glucose
What happens when glucose is severely limited?
- Energy is provided by metabolism of lipids – lipolysis and b-oxidation
- Overall demand is to synthesise glucose in the liver for essential functions
- All possible gluconeogenic precursors used by the liver, including oxaloacetate
What if there is a insufficient oxaloacetate in severe glucose limitation?
- If there is insufficient oxaloacetate to react with the acetyl CoA the acetyl CoA is converted to Ketone Bodies
What 3 situations might cause insufficient oxaloacetate?
- diabetes
- ketosis
- twin lamb disease
these are all metabolic diseases
The acetyl CoA which cannot enter the TCA cycle is converted to ketone bodies in the liver, what are the 3 ketone bodies?
- Acetone
- Acetoacetate
- 3-hydroxy butyrate
