Sean - B-oxidation

Question 1

What is B-oxidation?

Answer 1

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

Question 2

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

Answer 2

B oxidation ->

Krebs cycle/TCA cycle ->

Electron transport chain

Question 3

How many reactions are there in B-oxidation?

Answer 3

Four

Question 4

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

Answer 4

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

Question 5

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

Answer 5

They produce a 2 carbon molecule called acetyl-coA

Question 6

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

Answer 6

8 molecules of acetyl Co A

Question 7

What happens to Acetyl CoA?

Answer 7

It enters the Krebs Cycle

Question 8

What is the simplest form of B-oxidation?

Answer 8

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

Question 9

What conditions complicate B-oxidation?

Answer 9

An uneven number of carbons to the chain

The presence of double bonds

Question 10

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

Answer 10

1 molecule of acetyl CoA

Question 11

Name the energy carriers involved in B oxidation

Answer 11

NAD+

FAD

Question 12

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

Answer 12

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

Question 13

What enzyme catalyses reaction one?

Answer 13

Acyl-coA dehydrogenase

Question 14

What does Acyl-coA dehydrogenase do?
(2)

Answer 14

Enzyme in reaction one

Forms a double bond by removing 2 H

Question 15

What happens to the two hydrogens removed at reaction 1?

Answer 15

They are given to energy carrier FAD to form FADH2

Question 16

What does FADH2 do?

Answer 16

Carries electrons to the electron transport chain

Question 17

What type of reaction is reaction one?

Answer 17

Dehydrogenation/Oxidation reaction (removal of hydrogens)

Question 18

What happens in reaction 2?
(3)

Answer 18

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)

Question 19

What enzyme catalyses reaction 2?

Answer 19

Enoyl-CoA hydratase

Question 20

What does enoyl-CoA hydratase do?

Answer 20

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

Question 21

What type of reaction is reaction 2?

Answer 21

Hydration reaction

Question 22

What happens in reaction 3?
(4)

Answer 22

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

Question 23

What enzyme catalyses reaction 3?

Answer 23

B-hydroxyacyl-CoA dehydrogenase

Question 24

What does B-hydroxyl-CoA-dehydrogenase do?

Answer 24

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

Question 25

What is the energy carrier in reaction 3?

Answer 25

NAD+

Question 26

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

Answer 26

NAD+ accepts two hydrogens to form NADH (reduction) NADH then transports it's two electrons to the energy transport chain

Question 27

What type of reaction is reaction 3?

Answer 27

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

Question 28

What happens in reaction 4? (6)

Answer 28

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)

Question 29

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

Answer 29

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

Question 30

What are isoenzymes?

Answer 30

Different molecular forms of the same enzymes produced by different genes

Question 31

What does the type of isoenzyme used depend on?

Answer 31

The length of the fatty acid chain

Question 32

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

Answer 32

The mitochondrial membrane

Question 33

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

Answer 33

The mitochondrial matrix

Question 34

What is a thiolation reaction?

Answer 34

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