Catabolism of Fats Flashcards
Fat is the most _________________ store of energy
concentrated
Why do fats have a greater delta E
due to reduced carbon atoms in fatty acids (no oxygen in fattys acids, only carbons)
How are fats very chemically reduced
most of the carbon atoms are CH2 so it releases the max amount of energy when oxidized to CO2 (compared to sugars that are mostly partially oxidized already)
Since fats are very hydrophobic, they can be stored nearly ____________ free
water free
- unlike carbs, which carry much more water (less energy dense)
How much (approx) does a human need of fuel from energy reserves (in kJ)
8000 a day
What is the first stage in the cycle that breaks down fatty acids
beta oxidation
What are the 3 stages (in order) that break down fatty acids
- beta oxidation
- the TCA cycle
- Electron transport chain
Who identified beta oxidation
Franz Knoop
How did Franz Knoop discover beta oxidation
tagged terminal (omega) carbons in fatty acids with a phenyl group and fed to dogs, then collected their urine to examine the aromatic products
What is the pattern in fatty acid catabolism
catabolized 2 carbons at a time
Where are fatty acids prepped for catabolism by being turned into fatty acyl CoA (with the help of CoA cofactor and acyl-CoA synthetase)
in the outer mitochondrial membrane
What is the equation turning fatty acids into fatty acyl CoA
Fatty acid + CoA + ATP = Fatty acyl CoA + AMP + PPi
What are the two steps of converting fatty acids to fatty acyl CoA
- the nucleophilic oxygen of the fatty acid attacks the alpha phosphate in ATP, to break off the beta and gamma phosphates (forming PPi and an acyl adenylate)
- coenzyme A acts as the nucleophile and attacks the acyl adenylate (fatty acid + alpha phosphate) and AMP acts as the leaving group
overall produces fatty acyl CoA, AMP, and PPi
What is the overall energy lost by the conversion of fatty acid to fatty acyl CoA
delta G = -19 kJ/mol (from formation of PPi)
delta G = -15 kJ/mol (from formation of fatty acyl CoA)
overall delta G = -34 kJ/mol
Where does beta oxidation take place
mitochondrial matrix
Why does beta oxidation take place in the mitchouchonrial membrane
the outer membrane is freely permeable to small molecules and ions, but the inner membrane is highly insoluble to most solutes
- so the mitochondrial matrix has a very different chemical composition then the bulk of cytosol
Fatty acids with more than 12 carbons are too large to pass the membrane, so what carrier is needed
acyl-carnitine / carnitine transporter
What form must fatty acids be in to transport across the membrane
in the form of fatty acyl-carnitine
What are the 4 steps of beta oxidation
oxidation
hydration
oxidation
thiolysis
Each pass through beta oxidation results in how many acetyl CoA
each pass results in one acetyl CoA produced
What is step 1 of beta oxidation
oxidation by FAD
- forms a double bond between the alpha and beta carbons of fatty acyl CoA
loss of hydrogen from fatty acid, gets put onto FAD to become FADH
What enzyme is involved in the first step of beta oxidation
acyl-CoA dehydrogenase
What is step 2 of beta oxidation
water is added
- provides an alcohol to the beta carbon
rids of the double bond and results in a hydroxyl on the third carbon
What enzyme is involved in the second step of beta oxidation
enoyl-CoA hydratase
