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34 Cards in this Set
- Front
- Back
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What tissues/cells dont use FAs during fasting as energy source?
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brain
RBCs adipocytes intestinal mucosal cells |
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What stimulates and cleaves FAs from TAGs?
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high epinephrine and glucagon:insulin ratio
hormone sensitive lipase cleaves TAGS |
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How are FAs transported in blood?
What takes them into the cell? |
bound to albumin
fatty acid binding protein |
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Where are FAs mainly degraded? Where else?
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mitochondria
also peroxisomes and ER |
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How are FAs activated?
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FA --fatty acyl CoA synthetase --> fatty acyl coA
*requires 2 high energy phosphate bonds |
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What can activated FAs be used for?
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energy (B oxidation, ketogenesis)
storage as TAGs (adipocytes) membrane lipids |
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How do long and medium chain FAs pass through inner mito membrane?
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medium chains = C6-C12 pass freely
long chains (c12+) in carnitine conjugated form - need carnitine palmitoyl transferase 1 (CPT1) *committed and regulatory stp, by malonyl CoA then need CPTII to get into inner membrane |
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what 2 things are required for carnitine synthesis?
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lysine
s-adenosyl methionine (methyl donor) |
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What happens in deficiencies of carnitine metabolism?
How do we treat it? |
cant degrade long chain FAs > hypoketotic hypoglycemia > elevated liver enzymes and ammonia (liver damage)
treat with high carb, low fat diet with medium chain FAs (eliminate long chain) |
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if carnitine palmitoyl transferase I was deficient, what would happen to carnitine? what about C16-18acylcarnitine?
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carnitine elevated
C16-18 low |
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Where does B oxidation take place?
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mitochondrial matrix
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What is generated every cycle? Where do they go next?
how much does length decrease by after each cycle? |
1 cycle > FADH2 and NADH (> ox phos > ATP), acetyl coA (>TCA cycle > energy, or ketone body synthesis in liver)
decreases by 2C every cycle |
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what are the 4 steps of B oxidation?
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1. fatty acyl coA --acyl coA dehydrogenase + FAD --> fatty enoyl CoA + FADH2
2. --enoyl CoA hydratase + H2O--> B hydrozy acyl coA 3. --B hydrozy acylCOA dehydrogenase + NAD --> Keto acyl coA + NADH 4. --B keto thiolase --> fatty acyl coA (2C shorter) + acetyl coA |
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formula for # ATPs produced by degradation of saturated even chain length FA
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(n-1) x 14 + 10 - 2 = total ATP
n=number of cycles (divide C by 2) |
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what is net ATP production from complete B oxidation of palmitate C16 molecule?
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106
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what happens when unsaturated FAs are B oxidized (have cic double bond)?
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when reaches the cis bond it is isomerized to trans bond and b oxidation continues
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What does the last cycle of odd chain FAs oxidation produce?
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1 acetyl coA + 1 propionyl coA (3c)
this is degraded to succinyl coA > TCA cycle deficiencies > acidemias |
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What happens in medium chain acyl coA dehydrogenase (MCAD) deficiency?
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elevated c6-c10 acylcarnitine levels in plasma and urine
elevated c6-c10 dicarboxilic acids in urine (w-oxidatoon) similar onset and symptoms as carnitine deficiency, but tell differency by metabolites treat with glucose and carbohydrate rich diet |
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where are medium chain FAs degraded?
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mitochondria
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How is B oxidation regulated?
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FA availability > more FAs released from fat > more B oxidation
malonyl coA inhibits CPT1 -acetyl coA carboxylase --> malonyl coA --> inhibits when there is high insulin:glucagon (well fed) high AMP = not inhibites when ATP:ADP high > inhibits e-tc > not enough NADH and FADH2 being produced to fuel B oxidation |
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where does w-oxidation take place? what does it produce?
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ER
dicarboxylic acids, which can undergo mitochondrial B oxidation |
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when is w-oxidation important?
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when B oxidation is deficient
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What type of FAs do peroxisomes degrade?
where is this most important? |
very long chain (C20+)
important in nervous system shortened and sent to mito |
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what is the main difference between mito and peroxisomal degradation FAs?
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peroxisomal does not produce FADH2 like mito does, produces H2O2
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What is deficient in refsum disease?
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phytanic acid hydroxylase
nervous system disorfer |
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what is deficient in sellwagger syndrome?
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deficient peroxisome biogenesis > prevents degradation of very long chain and branched chain FAs
is a nervous system disorder because these are very abundant there |
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where does ketone body synthesis take place?
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liver
converts acetyl coA into metabolites that other tissues can use for energy (convert it back and go through TCA cycle) |
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What uses ketone bodies as main energy source? What cant use them at all?
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brain - only uses them
liver and RbCs cant use them because missing an enzyme to get acetyl coA back |
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what are 3 types of ketone bodies?
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acetoacetate
B hydrozybutyrate acetone |
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in a low glucose body what would be an important energy source for the brain?
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B hydrozybutyrate
or acetoacetate (ketone bodies) |
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explain ketone body synthesis
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2 acetyl co A
--thiolase--> acetoacetyl coA --HMG coA synthase --> HMG CoA --HMC CoA lyase --> acetyl coA + ketone body |
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How are ketone bodies used for energy?
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transported to peripheral tissues
broken down into 2 acetyl coA go through TCA cycle |
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How is ketone body synthesis regulated?
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rate of B oxidation regulates amount of acetyl coA
high NADH: NAD > malate-oxaloacetate reaction reversed > cant eneter TCA cycle to make ketone bodies |
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what energy metabolite increases the most when fasting?
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B hydroxybutyrate
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