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What enzyme hydrolyzes triacylglycerids to form a free fatty acid? Is this enzyme activated by phosphorylation or dephosphorylation
Lipase: TAG --> DAG + FFA (repeat until resulting in glycerol + FFA).
Activated by phosphorylation from PKA
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How do high levels of free fatty acids affect the fatty acid mobalization?
High levels of FFA inhibit the cyclase and the lipase.
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How do FFA dissolve in the blood?
non covalent interaction with serum albumin
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What reactions do CAT 1 and CAT 2 catalyze? Where are these enzymes located
CAT 1 (outer membrane): fatty acyl coA+ carnatine --> fatty acyl carnitine + coASH
CAT 2 (inner membrane) fatty acyl carnitine + co ash --> fatty acyl co A + carnitine
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Locations of fatty acid activation for very long chain, long chain, medium chain, and short chain fatty acids
- >24C very long chain = peroxisomes
- 12-22C long chain = cytosol
- 6-10C medium chain = mitochondria
- <6 short chain = mitochondria
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How do short and medium chain fatty acids get into the mitochondria?
Diffuse through lipid bilayer--not translocase required.
These are activated in the mitochondria via fatty acyl coA synthetase.
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Process of liberating an Acetyl coA from fatty acetyl coA
1. oxidize between beta and alpha carbon to form double bond in trans formation (FAD -> FADH2)
2. Add water across double bond
3. Reduce (dehydrogenate) to creat a carbonyl on beta carbon (FAD -> FADH)
4. Cleave off acetyl coA by thiolytic reaction, resulting in a fatty acyl co A that has been reduced by 2 carbons + acetyl coA.
ATP per cleavage = 5
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Enzymes of B oxidation
- 1. oxidize w/ acetyl co A dehydrogenase
- 2. hydrate with hydratase
- 3. oxidize with L beta hydroxyacyl co A dehydrogenase
- 4. thiolytic cleavage (release acetyl co A) with thiolase
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How many ATP would you get from B oxidation of a 16C fatty acid (palmitate)
7 cleavages X 5 ATP = 35 ATP
8 acetyl co A for CAC X 12 ATP per round = 96 ATP
35+96=131 ATP
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In a odd number carbon beta oxidation, what is the name of the last molecule?
propyl co A
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How many ATP equivelents are used to activate a free fatty acid to fatty acyl co A?
2 ATP equivelents.
It's a 2 step reaction where a phosphate is cleaved off in each step.
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What does the enzyme 2,4 dienol co A reductase do?
Uses NADPH to reduce conjugate double bonds in poly unsaturated fatty acids during beta oxidation.
Reduces to one double bond.
Isomerase then puts bond in correct position.
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What step does a unsaturated fatty acid skip in beta oxidation
Skips the "creation" of a double bound--so does not reduce FAD to FADH2.
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Is there ATP production from B oxidation of very long chain fatty acids?
No--this process occurs in peroxisomes which do not have mitochondria.
Oxidation occurs until 8 carbons, and then fatty acid can be transproted to the mitochondria for further B oxidation.
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Zellwegers syndrom inhibits the breakdown of what?
Very long chain fatty acids.
Zellwegers = inabillity to make peroxisomes
(also presented in section 1, w/ inability to myelinate)
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Where are ketone bodies made?
Mitochondria matrix in the liver
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Can the liver use ketone bodies as a source of energy?
No
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What are ketone bodies?
Water soluble derivities of fatty acids derived from condensation of acetyl-coA's.
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How are beta hydroxybuterate and acetone formed from acetoacetate?
hydroxybuterate = acetoacetate is reduced by NADH to convert carbonyl to hydroxyl group
acetone = acetoacetate is decarboxylated to form acetone. Not a source of eneryg for body, exhaled through lungs.
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Why would a patient have sweet smelling breath?
From an over production of ketone bodies (specifically form acetone).
This occurs in uncontrolled type 1 diabetes..
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What enzymes convert 2 acetyl co As to ketone bodies?
- 1. Thiolase
- 2. HMG CoA synthetase
- 3. HMG co A lyase
Result = acetoacetate
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Step 1 of ketone body synthesis
Thiolase 2 acetyl co A together, eliminate coash
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Step 2 of ketone body synthesis
Add Acetyl CoA and eliminate coASH to form HMG coA
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Step 3 of ketone body formation
Get rid of another coASH to form acetoacetate
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Can fatty acids cross the blood brain barrier? Can ketone bodies?
No, fatty acids can't cross BBB. Yes, ketone bodies can cross BBB
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Why are the productio of ketone bodies "glucose sparing"?
Ketone bodies can cross the BBB. This means during fasting/starving, liver has to do less gluconeogenisis to keep brain "fed".
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Related to ketone bodies, what is one way NAD+ is regenerated in the liver?
Through conversion of acetoacetate to beta hydroxybutyrate.
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Does the brain get a larger benefit from using acetoacetate or from using beta hydroxybuterate?
Betahydroxybuterate becase to convert this to glucose in the brain, the first step is do oxidize the hydroxyl group , resulting in generation of 1NADH = 3ATP in ETC.
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How do you synthesize acetyl co A from b-hydroxybutyrate?
B hydroxybuterate is oxidzed for form NADH and acetoacetate.
acetoacetate accepts acetyl coA from succinyl co A (from CAC).
thiolase leaves teh 2 acetyl groups apart from each other to generate 2 acetyl co A molecules.
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Ketosis
When production of ketone bodies is high, but not change in pH.
Example: Adkins diet, startving
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ketoacidosis
When the production of ketone bodies is high AND there is a change in blood pH
examples: uncontrolled type 1 diabetes
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How does ketone body production spare amino acids?
By providing a source of energy to the brain and other tissues that takes some stress off gluconeogenisis.
Gluconeogenisis requires amino acids or pyruvate.
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Are fatty acids gluconeogenic?
Not usually.
FFA can be broken down to acetyl co A, which cannot be converted back to pyruvate in PDH (irreversable reaction).
Exception: The last cleavage of a FFA may result in a 3 carbon propionyl co A
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What vitamin does propionyl co A carboxylase need, and what reaction does it carry out?
Needs biotin.
Propionyl co A + ATP + "CO2" --> methylmalonyl co A + ADP + P1
Next part of reaction is a mutase containing vitamin b12=biotin
end result is succinyl co A
(similiar to pyruvate carboxylase)
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