Question

Oxidation of fatty acids with a methyl group at the 3-position, such as Phytanic acid, starts with ____.

• A. alpha oxidation
• B. beta oxidation
• C. omega oxidation
• D. glyoxalate cycle

Hint:

A methyl branch at the beta carbon blocks normal beta oxidation, so a different pathway must act first.

Answer 1

The Correct Option is A

Step 1: Normal fatty acid breakdown happens through beta oxidation, which removes two carbon units at a time by acting on the beta carbon, the third carbon from the carboxyl end.

Step 2: Phytanic acid has a methyl branch sitting exactly at that beta carbon position, and this branching blocks the enzyme machinery of beta oxidation from working directly on it.

Step 3: To get around this block, the cell first performs alpha oxidation, which removes a single carbon from the carboxyl end and repositions the methyl branch so that the molecule can subsequently proceed through normal beta oxidation.