(MSCDFSM) Nutritional Biochemistry (TMA-2) ANSWER 2017

Q7. a) List the three steps involved in the oxidation of fatty acids? Highlight the role of 4 enzymes and steps involved in beta oxidation.

ANS- The major reaction to produce energy using lipids is in the fatty acid spiral. The beta oxidation of fatty acids occurs by the removal of two carbons at a time as acetyl CoA in a spiral type reaction. These reactions occur in the mitochondria and thus are closely associated with the electron transport chain to produce energy in the form of ATP. In addition, the acetyl CoA which is produced is feed mostly into the citric acid cycle.

The overall reaction is:

fatty acid CoA + NAD+ + FAD ---> acetyl CoA + NADH + H+ + FADH2

Steps of Beta-Oxidation

Every good play has a plot. The main plot of beta-oxidation is that the fatty acids are looking to change themselves, or be broken down. Before we get to the main plot, a little bit of exposition is needed to set the scene. The enzyme, acyl-CoA ligase, uses adenosine triphosphate, or ATP, to join a fatty acid with CoA. They form a new happy molecule called acyl-CoA. It is as acyl-CoA that the fatty acids are able to broken down in the mitochondrial matrix.

There are four main steps—or acts—in beta-oxidation:

1.Loss of hydrogens

2.Addition of water

3.Loss of another hydrogen

4.Addition of another CoA

In the first step, two carbons in the long fatty acid chain, called the alpha and beta carbons, of acyl-CoA are exposed. Acyl-CoA then is attacked by the enzyme, acyl-CoA dehydrogenase, which steals two hydrogens from the alpha and beta carbons.

The two hydrogens are passed off to FAD+, which changes it to FADH2. FADH2 continues on to aid in energy production. In the meantime, acyl-CoA changes its name to alpha beta-Enoyl-CoA in honor of the lost hydrogens.