Biochemistry-Beta Oxidation I Flashcards
In fat you get 9 cal of energy/gram of fat, in carbohydrate you get 3 cal/g. Why is this?
It has more electrons that can interact with O2 in the ETC.
Why is glycogen not as good of an energy store as fat?
Fat is anhydrous and you need less of it because it does not bind water.
What are the main fatty acids we get in our diet?
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Your child has to get up to eat at all hours of the night or else she becomes hypoglycemic. What metabolic process is deficient?
Fatty acid metabolism. This is what allows us to sleep through the night without eating.
What carries fatty acids through the blood?
Albumin
What are the different fatty acid lengths that require different metabolism?
VLCFA (>20) LCFA (12-20) MCFA (6-12) and SCFA (<6)
How is the fatty acid converted to the activated CoA derivative?
Fatty acyl CoA synthetase binds the fatty acid to the alpha phosphate of ATP. Pyrophosphate is released and the AMP-Fatty Acid compound is then attacked by CoASH and displaced AMP to make your fatty acyl CoA, AMP and two Pi molecules.
How is fatty-acyl CoA brought into the mitochondrial matrix?
The fatty acyl-CoA gets into the inter membrane space. Carnitine palmitoyle transferase I (CPT 1) kicks out the CoA and adds carnitine to form fatty acylcarnitine. Fatty acylcarnitine is recognized by Carnitine acylcarnitine translocase (membrane antiport into mitochondrial matrix) and takes fatty acyl carnitine in while pushing a carnitine out. The reverse reaction is done by CPT II in the mitochondrial matrix making fatty acyl CoA and carnitine.
Once the fatty acyl CoA is in the mitochondrial matrix, how is it converted to Acyl CoA fragments?
Acyl CoA dehydrogenase sends FAD to remove 2 H’s between the alpha and beta carbons of the fatty acid, forming a double bond (enol) and FADH2. Enoyl CoA hydratase adds H2O to the trans fatty enoyl CoA so the hydroxyl group is on the beta carbon to form L-beta-Hydroxy acyl CoA. L-beta-Hydroxy acyl CoA’s hydroxy group is then oxidized by beta-hydroxy acyl CoA dehydrogenase’s NAD to form NADH and beta-keto acyl CoA. Beta-keto acyl CoA is then thiolytically cleaved by CoA of beta-keto thiolase to form a new fatty acyl Co A and Acetyl CoA. This is repeated again and again and again.
What reactions of beta oxidation are similar to other metabolic reactions?
Succinate -> Fumarate by succinate synthetase in TCA cycle is similar to Fatty Acyl CoA -> Trans Fatty Enoyl CoA by acyl CoA dehydrogenase. Fumarate -> Malate by fumarase in TCA cycle is similar to trans fatty enoyl CoA -> L-beta-hydroxy acyl CoA by enoyl CoA hydratase. Malate -> Oxaloacetate by malate dehydrogenase is similar to beta-keto acyl CoA -> Fatty acyl CoA and Acetyl CoA by beta-keto thiolase.
Why can someone have perfectly normal functioning acyl CoA dehydrogenase enzymes in some tests and nonfunctional enzymes in another test?
Our body has different beta-oxidation enzymes specific for the length of the fatty acid. A person with enzymes with the same function for a long chain fatty acids may not have functional enzymes for short chain fatty acids.
What is the overall input and output of beta oxidation of palmitoyl-CoA?
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What is the purpose of have enzymes like enoyl CoA isomerase and 2,4 dienoyl reductase?
To resolve problems such as intermediates with double bonds in the wrong place, cis double bonds or conjugated double bonds (makes molecule rigid).
How would beta-oxidation of linoleoyl CoA take place?
The first three steps will proceed as normal. Once you hit the double bond, enoyl CoA isomerase comes to the rescue and moves the 3-4 double bond to positions 2-3. This creates a normal intermediate and oxidation continues as normal until you hit the 2-3 double bond with the 4-5 double bond. 2,4-dienoyl CoA reductase converts these two double bonds to a single 3-4 double bond. Enoyl CoA isomerase moves the 3-4 double bond to a 2-3 double bond and oxidation can resume again as normal.
How does 2,4-dienoyl CoA reductase combine two double bonds into one?
NADPH donate a hydride across the 4-5 double bond and then takes an H from the 2-3 double bond to form a 3-4 double bond.
What are the products of odd-chain fatty acid oxidation?
You can use acetyl CoA but need to get propionyl CoA out of your system
How is propionyl CoA metabolized?
It is first carboxylated to form D-methylmalonyl CoA by propionyl CoA carboxylase (biotin). D-methylmalonyl CoA is converted to its epimer by mehtylmalonyl CoA epimerase. L-methylmalonyl CoA is then converted to Succinyl CoA by methylmalonyl CoA mutase (coenzyme B12). Succinyl CoA then plugs into the TCA cycle or gluconeogenesis.
The first step in VLCFA metabolism involves FAD in peroxisomes. How does the peroxisome recycle FAD?
Oxygen is oxidized to form H2O2 and FADH2 by FAD Oxidase
If your neighbor is syphoning gasoline and accidentally ingests some. How will his body metabolize the ingested gasoline?
It is pure hydrocarbon so you will need Cyt P450 to insert and oxygen via ROS so it can be further metabolized.
How do peroxisomes go about alpha-hydroxylation?
Multiple additions of ROS causes CO2 to break off of the molecule until it is fully metabolized.
Why can’t your mitochondria just oxidize branched chain fatty acids you get from vegetables?
After dehydrogenation with FAD to form the double bond, the alcohol group is added to the same carbon with the methyl group. This hydroxy group can no longer be oxidized because there are already 4 bonds to that carbon.
How does our body get rid of branched-chain fatty acids?
Do an alpha-oxidation to shorten the chain by one carbon and then proceed with beta-oxidation. Many of your products will be propionyl-CoA and you have to dispose of it through its proper pathway.
What happens to the products of omega-oxidation?
They go into the mitochondrial matrix and undergo a few rounds of beta-oxidation until they form short-chain dicarboxilic acids that can be excreted in the urine. This type of reaction is very common in getting rid of drugs.
