FA Oxidation

Question 1

Dietary lipids are taken up and then stored as?

Answer 1

Triacylglycerol (TAG)

Question 2

What are Triacylglycerols catabolised to?

Answer 2

Fatty acids and glycerol by Lipase.

• Glycerol can be metabolised into triose phosphates found in glycolysis
• Fatty acids are metabolised
by β-oxidation in the steps that will follow

Question 3

Give step one of Glycerol metabolism.

Glycerol comes from catabolism of TAGs

Answer 3

Glycerol is converted to L-Glycerol 3-phosphate using glycerol 3-phosphate dehydrogenase.

Question 4

Give step two of Glycerol metabolism.

Answer 4

L-Glycerol 3-phosphate is converted to Dihydroxyacetone phosphate by glycerol 3-phosphate dehydrogenase.

Question 5

Give step three of Glycerol metabolism.

Answer 5

Dihydroxyacetone phosphate is converted to D-Glyceraldehyde 3-phosphate by Triose phosphate Isomerase.

**D-Glyceraldehyde 3-phosphate then enters glycolysis*

Question 6

Where does FA oxidation take place?

Answer 6

In the matrix of the mitochondrion.

Question 7

True or false? FA of 12C or less move freely, whereas, over 12C require a transporter.

Answer 7

True.

Question 8

The Carnitine shuttle moves FAs and consists of three parts, these are?

Answer 8

• acyl-CoA synthetase
  • carnitine acyl-transferase 1
  • carnithine acyl-transferase 2

Question 9

Give the equation for the activation of fatty acids.

Answer 9

Fatty acid + CoA + ATP <——> Fatty acyl-CoA + AMP + 2Pi

• Thus, acyl–CoA synthetases catalyze the formation of a thioester linkage between the fatty acid carboxyl group and the thiol group of coenzyme A to yield a fatty acyl– CoA, coupled to the cleavage of ATP to AMP and PPi.

Question 10

Give step one in the mechanism of acyl CoA synthetase.

Answer 10

The carboxylate ion of the fatty acid is adenylated by ATP to form a fatty acyl-adenylate and PPi using fatty acyl-CoA synthetase. The PPi is immediately hydrolyzed to two molecules of Pi.

Question 11

Give step two in the mechanism of acyl CoA synthetase.

Answer 11

The thiol group of coenzyme A attacks the acyl-adenylate (a mixed anhydride), displacing AMP and forming the Thioester fatty acyl-CoA by the enzyme fatty acyl-CoA synthetase.

Question 12

Describe the reaction that allows FAs to pass the outer mitochondrial membrane.

Answer 12

The fatty acyl-CoA is temporarily attached to the hydroxyl group of Carnitine for transport, where the reaction is catalyzed by Carnitine actl-transferase 1 (CPT1) and is a transesterification

Question 13

After the FA has passed the outer membrane how does it enter the matrix?

Answer 13

Passive transport via the acyl-carnitine/carnitine cotransporter.

Lastly, the fatty acyl portion of the molecule is transferred from carnitine to the mitochondrial
pool of CoA-SH

• This compartmentalisation allows the cell to maintain separate pools of CoA as well as fatty acyl-CoA which maintain different functions in the cell

Question 14

β-oxidation of saturated fatty acids occurs in 4 steps in the mitochondrion. These are?

Answer 14

• oxidation (acyl-CoA dehydrogenase)
• hydration (enoyl-CoA hydratase)
• oxidation (β hydroxyacyl-CoA dehydrogenase)
• cleavage (acyl-CoA acetyltransferase)

Question 15

Give step of saturated FA oxidation of Palmitoyl-CoA.

Answer 15

Palmitoyl-CoA is converted to trans-D2-Enoyl-CoA using acyl-CoA dehydrogenase.