Chapter 24, Problem 24.63AP

Interpretation Introduction

Interpretation:

The two differences in the reactions for fatty acid synthesis and the reaction for fatty acid degradation should be described.

Concept introduction:

Fatty acids are aliphatic mono-carboxylic acids that are mostly obtained from the hydrolysis of natural fats and oils. They have a general formula $R-{\left(C{H}_2\right)}_n-COOH$, n is mostly an even number of carbon atoms (4 to 20) with a few exceptions that have an odd number.

$\text{β-oxidation}$ is the oxidation and splitting of two carbon units at $\text{β}$- carbon atom. This results in sequential removal of 2 carbon fragments as acetyl CoA until the complete oxidation of fatty acids.

The four important steps of $\text{β-oxidation}$ are,

Step 1: Dehydrogenation of the fatty acyl-CoA to make ‘trans’ double bond between $\text{α}$ and $\text{β}$ carbon.

• Short, medium and long chain acyl-CoAdehydrogenases
• Electron removed transferred to FAD

Step 2: Hydration of the double bond.

Step 3: Dehydrogenation of the $\text{β-hydroxyl}$ group to a ketone.

• Electron removed transferred to $NA{D}^{+}$

Step 4: Acylation-addition of CoA and production of and production of acetyl-CoA

Lipogenesis is the metabolic pathway by which fatty acids are synthesized from acetyl-CoA.

Lipogenesis requires;

Synthesis of fatty acids and glycerol

Activation of fatty acids by CoA and glycerol by glycerokinase

The combination of activated fatty acids and activated glycerol to produce TAG (triacylglycerol)