Fatty Acid Metabolism (beta-oxidation) Flashcards
Summarise the metabolism of glycerol in the liver.
Enters the glycolysis pathway by conversion into glucose by gluconeogensis.
Summarise the metabolism of glycerol in most tissue.
Enters the glycolysis pathway where its converted to pyruvate which enters the TCA cycle.
Where in the cell does β-oxidation of fatty acids occur?
In the Mitochondrial matrix
How many reactions occur in β-oxidation?
Four
How are long chain fatty acids activated?
Reaction with CoA to form a thiol ester (fatty acyl CoA). Requires ATP.
RCOO- + ATP + CoA-SH > RCO-S-CoA + AMP +2Pi
What system transports fatty-acyl CoA into the mitochondrial matrix?
The carnitine shuttle system
What is the biochemical role of carnitine?
Transport of fatty-acyl CoA into the mitochondrial matrix.
By what mechanism does carnitine transport fatty-acyl CoA into the mitochondrial matrix?
Carnitine + fatty-acyl CoA > carnitine-acyl complex + CoA(catalysed by carnitine transferase I)
carnitine-acyl complex is transport into mitchondrial matrix through transporter proteins.
carnitine acyl complex is reacted with CoA to reform the fatty-acyl CoA and release carnitine. Catalysed by carnitine transferase II
What enzyme catalyses the cytosolic reaction of carnitine + fatty-acyl CoA to form the carnitine-acyl complex?
Carnitine transferase I
What enzyme catalyses the reaction in the mitochondrial matrix that release carnitine and regenerates fatty-acyl CoA?
Carnitine transferase II
Name the 4 stages of β-oxidation in order.
- Oxidation
- Hydration
- Oxidation
- Thiolysis
Describe the first stage in β-oxidation of fatty acids.
Oxidation: alkane > alkene Fatty-acyl CoA > Enoyl-CoA -CH2-CH2- > -HC=CH- FAD > FADH2 Catalysed by acyl-CoA dehydrogenase.
Describe the second stage in β oxidation of fatty acids.
Hydration: alkene > alcohol
Enoyl-CoA > Hydroxyacyl-CoA
-HC=CH- > -CHOH-CH2-
Catalysed by Enoyl-CoA hydratase
Describe the third stage in β oxidation of fatty acids.
Oxidation: alcohol > ketone Hydroxyacyl-CoA > Ketoacyl CoA -CHOH-CH2- > -C=O-CH2 NAD+ > NADH Catalysed by Hydroxyacyl-CoA dehydrogenase
Describe the forth stage of β oxidation of fatty acids.
Thiolysis: (using CoA)
Ketoacyl CoA > Fatty-acyl CoA + acetyl CoA
Catalysed by β-ketoacyl-CoA thiolase
What happens to the acetyl CoA produces in β-oxidation?
Enters the TCA cycle.
What happens to the fatty-acyl CoA that is produced in β-oxidation?
Re-enters the beta-oxidation pathway to produce acetyl CoA. 2 carbons removed each round.
What happens to odd chain fatty acids?
Broken down until 3 carbon propionyl CoA remains. Propionyl CoA is broken down to succinate CoA which enters the TCA cycles.
What is the 3 carbon product of breakdown of odd chain fatty acids?
Propionyl- CoA
What enzyme catalyses the oxidation of fatty-acyl CoA to Enoyl-CoA?
acyl-CoA dehydrogenase
What enzyme catalyses the hydration of Enoyl-CoA to Hydroxyacyl-CoA?
Enoyl-CoA hydrolase
What enzyme catalyses the oxidation of Hydroxyacyl-CoA to Ketoacyl-CoA?
Hydroxyacyl-CoA dehydrogenase
What enzyme catalyses the thiolysis of Ketoacyl-CoA into a fatty-acyl CoA and acetyl CoA with the addition of CoA?
β-Keto-acyl CoA thiolase
What would be the energy yield of a 16 carbon fatty acid?
-2 ATP for activation to form the fatty-acyl CoA
Forms 8 acetyl CoA molecules
Each produces 10 ATP
8x10 = +80 ATP
β-oxidation pathway = 1FADH2 + 1NADH
FADH2 = 2 ATP
NADH = 3 ATP
7 repeats of β-oxidation pathway = 5x7
=35 ATP
Total: -2+80+35 = 113 ATP
