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2nd half of FA metabolism- Biochem

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Describe 1st step of B-oxidation of very long chain FA in Peroxisomes?
1st step of of B-oxidation is catalized by an FAD containing oxidase. e- are transfered from FADH2 to O2 which is then reduced to H2O2

Takes place in peroxisome because H2O2 is produced
What are similarities & differences of mitochondrial vs peroxisomal B-oxidation?
Both generate FADH2 & NADH but
Peroxisomal is less efficient because FADH can’t get through peroxisomal membrane (must be oxidized by O2)
Why do peroxysomal B-oxidation?
very long chain FA cannot cross mit membrane, must be broken up by peroxysomes
Describe oxydation of phytanic acid?
a peroxysomal alpha hydroxylase oxidizes the alpha carbon so that B oxidation can occur.
Refsum's disease
alpha oxidase enzyme is defective so we cannot break down phytanic acid
w-oxidation of FA
converts FA to dicarboxylic acids. Results in DC urea. Which is diagnostic for problem w/ B oxidation
4 steps of B-oxidation
1)Oxidation (ACoA dehyd)
2)Hydration (enol CoA hyd)
3)Oxidation(B hydroxy CoA hyd)
4)Cleavage (B keto thiolase)
Metabolism of Monosaturated Fats
2-3 enol-CoA isomerase - converts cis bond to trans
Metabolism of Polyunsaturated Fats
2-3 enol-CoA isomerase - converts cis bond to trans
2-4 dienol Co A reductase – reduces one of the double bonds
Propynyl Co A pathway
Propionyl CoA to Succinyl CoA. 1st step involves Propionyl CoA carboxylase (ABC enzyme) conversionof Propionyl CoA to methmylmalonyl CoA. Last step involves methyl-Malonyl CoA mutase conversion of Methylmalonyl CoA to Succinyl CoA. This last enzyme requires B12 therefore build up of Methylmalonyl CoA is diagnostic for B12 deficiency.
ABC enzymes
ABC
Pyruvate carboxylase -
Acetyl CoA carboxylase -
Propionyl CoA carboxylase -
MCAD deficiency
B oxidation in liver tissue in order for gluconeogenesis – if can’t do B-oxidation – hypoglycemic shock;
Feed child, replenished glycogen stores, in night using glycogen stores, next morning feed – child never in hard glucagon world. Never know about deficiency. Using liver glycogen always. When glycogen stores don’t get built up child needs to do gluconeogenis need to do B oxidation – usually dies in middle of night.
3 ketone bodies:
1)Acetoacetate can covert to:
2)Acetone (volitile)
3)D-B Hydroxybutyrate (more stable)
Why are ketone bodies made in liver cells only?
HMG Co A synthase –makes ketone bodies and found only in liver mitochondria
Why are ketone bodies broken down in tissues other than the liver
B-ketoacyl- CoA transferase is found in mitochondria outside liver -allows extrahepatic tissues to break ketone bodies down
Fuel for Brain
1) 24 hours
2)day 2-7
3) After 1 week
1)glycogen
2) protein (mostly glucose from gluconeogenesis but some ketone bodies)
3)Fat & small amount of protein-mostly ketone bodies but some glucose from gluconeogenesis

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