B-Oxidation Flashcards
What is the process of producing energy using fatty acids
b-oxidation
What is b-oxidation
Metabolic pathway responsible for breaking down fatty acids to generate energy.
A series of 5 enzyme-catalyzed reactions that cleaves carbon atoms 2 at a time from the carboxyl end of a fatty acid and feeds it into the TCA
What is the principal storage form of energy for most animals
fatty acids in triglycerides - they store energy in
What is the difference between the ATP yield of b-oxidation and glycolysis
The energy yield per gram of fatty acid oxidized is greater than that per gram of carbohydrate oxidized
Steric acid (18:0) C18
ATP:C = 8:1
Glycolysis (C6)
ATP:C = 6:1
Why is the oxidation of water soluble glucose preferred over oxidation of FA
Much more energy is produced per mole of lipid however water soluble glycoses is still the preferred method because it can be moved around in aqueous solutions and can be transported with molecules easily. Where as lipids require lipoproteins to carry them from one place to another which requires energy itself.
What reaction pathway occurs after B-oxidation
citric acid cycle
What enzyme is used to break down lipids
Lipases are the key enzymes
How are triglycerides broken down initially
Triglycerides from adipocytes are emulsified (bile salts) and then lipases enzymatically cleave the fatty acid chains from the triglyceride proceeding TAG –> DAG –> MAG –> glycerol
What is the substances put into b-oxidation
Fatty acid and CoA
What is the product of B-oxidation
multiple Acetyl-CoA
how many steps are in b-oxidation
5 steps
From the b-oxidation of steric acid (C18) how much ATP is produced
146
How do the FA molecules get into the mitochondria matrix
carnitine shuttle
What energy molecules are used and produced in b-oxidation
Used - ATP, NAD, FAD
Produces , NADH, FADH2
Which step of b-oxidation is an oxidation and how is it an oxidation
Step 2 - as it involves the loss of 2 hydrogens to form a double carbon bond (C=C)
Step 4
What are the carnitine shuttles
Step 1 occurs in the cytosol and carnitine shuttles are a mechanism which transports the FA acyl CoA (activated FA) into the mitochondria
What is step 1 of b-oxidation
Investment Phase
-The fatty acid is added onto Coenzyme A resulting in a high energy thioester bond to the Fatty acid
- This is an investment phase as ATP is required to be hydrolyzed into AMP to release energy
- The product is known as a fatty acid acyl CoA
- This step happens only once
How many times does step 1 of B-oxidation occur
once
What is used to transport FA into the mitochondria
Carnitine Shuttles
What is step 2 of b- oxidation
Oxidation
-Oxidation of the fatty acid acyl CoA which results in the loss of 2 hydrogens and the formation of a double bond between the alpha and beta carbons
- Uses Acyl CoA dehydrogenase (loss of hydrogens)
- FAD is reduced to FADH2 using the 2 hydrogens lost, this will enable ATP to be harvested as the reduced electron carrier FADH2 will continue to produce ATP through oxidative phosphorylation
What is step 3 of b-oxidation
Hydration
Water is added across the carbon double bond between the a and b carbon
What is step 4 of b-oxidation
Oxidation
- Oxidation at the site of the b carbon
- NAD+ is reduced to NADH which will harvest energy from the reduced electron carrier NADH in oxidative phosphorylation where ATP will be created
What is step 5 of b-oxidation
Cleavage Reaction
- the release of the 2C acetyl group from the original carrier CoA
- C2 is attached to a second CoA
- Significant energy will be harvested when the Aceryl-CoA passed into TCA
- The remaining FA chain (n-2) is grafted onto the original CoA
What occurs with the shortened fatty acyl CoA at the end of step 5
further oxidized by cycling through reactions 2-5 until the fatty acid carbon chain is completely degraded to acetyl CoA (removed 2 carbons each cycle)
What is the general reaction of each step in b-oxidation
- Investment of ATP
- Oxidation
- Hydration
- Oxidation
- Cleavage
What step/s is the investment stage
step 1
What steps is harvesting reactions
2-5
What stage is cleavage reactions
5
Where does step 1 of b-oxidation occur
investment = cytosol
Where does harvesting steps 2-5 of b-oxidation occur
mitochondria matrix
Where does cleave step 5 of b-oxidation occur
mitochondria matrix
How many acteyl CoA is produced from b-oxidation
For every n-carbon fatty acid we produce n/2 acetyl CoA to send to the TCA
How many times does a FA go around the b- oxidation
(n/2 -1) times
What is the role of CoA in b-oxidation
- Activates the fatty acid by forming acyl-CoA
- Acyl-CoA serves as the substrate for the enzymes involved in b-oxidation
How much ATP does 1 cycle of b-oxidation produce
17
FADH2 –> 2 ATP
NADH –> 3 ATP
Acetyl CoA –> 12 ATP
