Lipid Mobilization and Fatty Acid Oxidation Flashcards
Where does beta-oxidation take place?
The mitochondrial matrix
Beta-oxidation of saturated fatty acids is a series of how many reactions?
4
How many carbons are removed during each beta-oxidation cycle?
2
How many beta-oxidation cycles are needed to completely degrade a saturated fatty acid that consists of 18 carbons?
8
Beta-oxidation of very long chain fatty acids takes place where?
Peroxisome
What is beta-oxidation?
Oxidation of saturated fatty acids
Series of 4 reactions
What are the end products of beta-oxidation?
Acyl CoA and Acetyl CoA
Acetyl CoA molecules are taken to citric acid cycle
What intermediates are produced in beta-oxidation?
FADH2 and NADH
How many ATPs are produced in one beta-oxidation cycle?
4
FADH2 produces 1.5, NADH produces 2.5
What are the reactions of beta-oxidation?
1) Acyl-CoA -> trans-alpha,beta-Enoyl-CoA
(FAD is converted to FADH2)
Enzyme: acyl CoA dehydrogenase
2) Enoyl CoA hydrase
3) beta-hydroxyacyl-CoA -> beta-ketoacyl-CoA
4) beta-ketoacyl-CoA thiolase cleaves beta-ketoacyl-CoA to Acyl CoA and Acetyl CoA
What is the ratio of ATP/carbon in fatty acids? What about in glucose?
- 6 ATP/carbon in FA
5. 5 ATP/carbon in carbohydrates
What is the number of ATP produced by oxidation of palmitoyl CoA?
108 (106 net)
How are 2 ATP lost? 1 ATP used to bring FA into cell, 1 ATP used to bring it into the mitochondrial matrix
How are unsaturated fatty acids oxidized?
Because of the cis double bonds, two additional enzymes/reactions are required to degrade these molecules. Cis form must be changed into trans form before oxidation can occur.
Enoyl-CoA-isomerase
Enoyl-CoA-hydrase
How are odd-chain fatty acids oxidized?
The last beta-oxidation cycle of the odd chain fatty acids yields one acetyl-CoA and one propionyl-CoA
What happens to the propionyl-CoA produced during odd-chain fatty acid oxidization?
It is converted to Succinyl-CoA and enters the citric acid cycle
How are branched-chain fatty acids oxidized?
Alpha-oxidation is the mechanism for degrading branched chain fatty acids (e.g. phytanic acids, from green vegetables)
After activation to a CoA derivative, the product can be degraded by beta-oxidation
How are long-chain fatty acids oxidized?
Beta-oxidation in peroxisomes shortens very long chain fatty acids without ATP synthesis
The resulting medium chain fatty acids are then further degraded in the mitochondria
The initial reaction produces peroxide, which can be dealt with by peroxisomal catalase to form H20
What is ketogenesis?
Excess acetyl-CoA are converted to acetoacetate, beta-hydroxybutyrate, and acetone. These molecules are called ketone bodies
Where are ketone bodies formed?
Matrix of liver mitochondria
What is ketosis?
2 acetyl-CoA condensed to form acetoacetyl-CoA
Acetoacetate/Acetoacetyl-CoA is spontaneously decarboxylated to form acetone
Occurs in starvation and uncontrolled diabetes
Cardiac and skeletal muscle use ketone bodies as energy. Brain does only during prolonged starvation
