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2.1 Biochemistry of Metabolism > Sean - B-oxidation > Flashcards

Sean - B-oxidation Flashcards

1
Q

What is B-oxidation?

A

The conversion of a fatty acyl-coenzyme A into acetyl-CoA with the release of energy

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2
Q

What 3 pathways are required for the complete catabolism of fatty acids to generate ATP?

A

B oxidation ->

Krebs cycle/TCA cycle ->

Electron transport chain

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3
Q

How many reactions are there in B-oxidation?

A

Four

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4
Q

In general, what happens in each round of the four reactions of B ocidation?

A

In each round, 2 x C atoms are removed from the fatty acid chain

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5
Q

What happens to the two carbons released from the fatty acid chain during B oxidation?

A

They produce a 2 carbon molecule called acetyl-coA

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6
Q

How many molecules of acetyl-CoA will a 16 carbon fatty acid produce?

A

8 molecules of acetyl Co A

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7
Q

What happens to Acetyl CoA?

A

It enters the Krebs Cycle

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8
Q

What is the simplest form of B-oxidation?

A

The metabolism of saturated fatty acids with an even number of carbons

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9
Q

What conditions complicate B-oxidation?

A

An uneven number of carbons to the chain

The presence of double bonds

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10
Q

How many molecules of acetyl CoA are produced from a round of B-oxidation?

A

1 molecule of acetyl CoA

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11
Q

Name the energy carriers involved in B oxidation

A

NAD+

FAD

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12
Q

What happens in the first B-oxidation reaction?
(3)

A

Acyl-CoA dehydrogenase catalyses the formation of a double bond at B carbon by removal of 2 H

The 2H are donated to FAD to form FADH2

Electrons are then transferred from FADH2 to the electron transport chain

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13
Q

What enzyme catalyses reaction one?

A

Acyl-coA dehydrogenase

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14
Q

What does Acyl-coA dehydrogenase do?
(2)

A

Enzyme in reaction one

Forms a double bond by removing 2 H

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15
Q

What happens to the two hydrogens removed at reaction 1?

A

They are given to energy carrier FAD to form FADH2

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16
Q

What does FADH2 do?

A

Carries electrons to the electron transport chain

17
Q

What type of reaction is reaction one?

A

Dehydrogenation/Oxidation reaction (removal of hydrogens)

18
Q

What happens in reaction 2?
(3)

A

H2O is added across the double bond between the alpha and beta carbons

Catalysed by enoyl-CoA hydratase

The hydroxyl group is always added to the B group (B-oxidation)

19
Q

What enzyme catalyses reaction 2?

A

Enoyl-CoA hydratase

20
Q

What does enoyl-CoA hydratase do?

A

Its add H2O across the double bond between the alpha and beta carbons -> putting the hydroxyl group on the B carbon (hence B-oxidation)

21
Q

What type of reaction is reaction 2?

A

Hydration reaction

22
Q

What happens in reaction 3?
(4)

A

Two hydrogens are removed from the B carbon to form a carboxyl group

Catalysed by B-hydroxyacyl-CoA dehydrogenase

NAD+ is reduced to NADH (accepts electrons)

NADH then donates it’s electrons to the electron transport chain to generate ATP

23
Q

What enzyme catalyses reaction 3?

A

B-hydroxyacyl-CoA dehydrogenase

24
Q

What does B-hydroxyl-CoA-dehydrogenase do?

A

It removes two H from the B carbon to form a carboxyl group

25
Q

What is the energy carrier in reaction 3?

A

NAD+

26
Q

What happens to NAD+ in reaction 3?
(2)

A

NAD+ accepts two hydrogens to form NADH (reduction)

NADH then transports it’s two electrons to the energy transport chain

27
Q

What type of reaction is reaction 3?

A

Dehydrogenation/Oxidation reaction i.e. the loss of hydrogens

28
Q

What happens in reaction 4?
(6)

A

The sulphur of a CoA-SH molecule attacks the chain (between a and B)

This causes the chain to split, with a 2 carbon acetyl group and a fatty acyl-CoA group being formed

The 2 carbon acetyl group covalently attaches to the CoA to form Acetyl Co-A

The fatty acyl-CoA will undergo B-oxidation again to produce more acetyl-CoA

The acetyl-CoA produced is fed into the citric acid cycle

Catalysed by thiolase (acyl-CoA acetyltransferase)

29
Q

What does thiolase (acyl-CoA acetyltransferase) do?
(2)

A

Causes the splitting of a 2 carbon acetyl group from a fatty acid chain

Catalyses the formation of acetyl CoA and fatty acyl Co A

30
Q

What are isoenzymes?

A

Different molecular forms of the same enzymes produced by different genes

31
Q

What does the type of isoenzyme used depend on?

A

The length of the fatty acid chain

32
Q

In general, fatty acyl-CoA chains smaller than 12 carbons are degraded by a set of isoenzymes produced where?

A

The mitochondrial membrane

33
Q

In general, fatty acyl-CoA chains bigger than 12 carbons are degraded by a set of isoenzymes produced where?

A

The mitochondrial matrix

34
Q

What is a thiolation reaction?

A

The addition of a group containing a sulphur molecule (SH-CoA)

2.1 Biochemistry of Metabolism (21 decks)

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