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Bioc 2580 > Catabolism of Fats > Flashcards

Catabolism of Fats Flashcards

1
Q

Fat is the most _________________ store of energy

A

concentrated

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2
Q

Why do fats have a greater delta E

A

due to reduced carbon atoms in fatty acids (no oxygen in fattys acids, only carbons)

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3
Q

How are fats very chemically reduced

A

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)

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4
Q

Since fats are very hydrophobic, they can be stored nearly ____________ free

A

water free
- unlike carbs, which carry much more water (less energy dense)

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5
Q

How much (approx) does a human need of fuel from energy reserves (in kJ)

A

8000 a day

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6
Q

What is the first stage in the cycle that breaks down fatty acids

A

beta oxidation

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7
Q

What are the 3 stages (in order) that break down fatty acids

A
  1. beta oxidation
  2. the TCA cycle
  3. Electron transport chain
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8
Q

Who identified beta oxidation

A

Franz Knoop

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9
Q

How did Franz Knoop discover beta oxidation

A

tagged terminal (omega) carbons in fatty acids with a phenyl group and fed to dogs, then collected their urine to examine the aromatic products

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10
Q

What is the pattern in fatty acid catabolism

A

catabolized 2 carbons at a time

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11
Q

Where are fatty acids prepped for catabolism by being turned into fatty acyl CoA (with the help of CoA cofactor and acyl-CoA synthetase)

A

in the outer mitochondrial membrane

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12
Q

What is the equation turning fatty acids into fatty acyl CoA

A

Fatty acid + CoA + ATP = Fatty acyl CoA + AMP + PPi

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13
Q

What are the two steps of converting fatty acids to fatty acyl CoA

A
  1. 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)
  2. 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

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14
Q

What is the overall energy lost by the conversion of fatty acid to fatty acyl CoA

A

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

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15
Q

Where does beta oxidation take place

A

mitochondrial matrix

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16
Q

Why does beta oxidation take place in the mitchouchonrial membrane

A

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

17
Q

Fatty acids with more than 12 carbons are too large to pass the membrane, so what carrier is needed

A

acyl-carnitine / carnitine transporter

18
Q

What form must fatty acids be in to transport across the membrane

A

in the form of fatty acyl-carnitine

19
Q

What are the 4 steps of beta oxidation

A

oxidation
hydration
oxidation
thiolysis

20
Q

Each pass through beta oxidation results in how many acetyl CoA

A

each pass results in one acetyl CoA produced

21
Q

What is step 1 of beta oxidation

A

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

22
Q

What enzyme is involved in the first step of beta oxidation

A

acyl-CoA dehydrogenase

23
Q

What is step 2 of beta oxidation

A

water is added
- provides an alcohol to the beta carbon

rids of the double bond and results in a hydroxyl on the third carbon

24
Q

What enzyme is involved in the second step of beta oxidation

A

enoyl-CoA hydratase

25
Q

What is step 3 of beta oxidation

A

oxidation of the alcohol via NAD+
- NAD removes the hydrogens on carbon 3 resulting in a double bonded oxygen only

NAD picks up PAIR of hydrogens to become NADH+H

26
Q

What enzyme is involved in the third step of beta oxidation

A

beta-hydroxyacyl-CoA dehydrogenase

27
Q

What is step 4 of beta oxidation

A

thiolysis
- lysis of the bond between alpha and beta carbons

a cut is made between the second and third carbons on the chain to remove the alpha and beta carbons and restart beta oxidation

28
Q

What enzyme is involved in the fourth step of beta oxidation

A

thiolase

29
Q

Each round of beta oxidation produces _______ acetyl CoA and shortens the fatty acid by _______ carbons

A

produces 1 acetyl CoA
reduces the strand by 2 carbons

30
Q

How many FADH2 produced in each turn of beta oxidation

A

1

31
Q

How many NADH is formed in each turn of beta oxidation

A

1

32
Q

Where do the reduced products and CoA go to be oxidized

A

NADH and FADH2 are oxidized in the electron transport chain
Acetyl CoA is oxidized in the TCA cycle

Bioc 2580 (16 decks)

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