Unfortunately, the provided reference only discusses fatty acid synthesis generally, and doesn't provide information specifically about essential fatty acid biosynthesis. To fully answer this question, we need to clarify what makes a fatty acid "essential".
Essential fatty acids are fatty acids that cannot be synthesized by the human body and must be obtained from the diet. The two primary essential fatty acids are:
- Alpha-linolenic acid (ALA): An omega-3 fatty acid.
- Linoleic acid (LA): An omega-6 fatty acid.
Because humans lack the enzymes to introduce double bonds beyond the carbon-9 position in fatty acids, we cannot synthesize these. Instead, we rely on plants (and ultimately, the animals that consume plants) to create them. The biosynthesis of these essential fatty acids, therefore, occurs primarily in plants and certain microorganisms, not in humans. The reference provided focuses on the general process of fatty acid synthesis within a cell, not on the specific pathways that create ALA and LA de novo (from scratch).
Here's a more complete picture of fatty acid biosynthesis, incorporating the concept of essentiality:
The general fatty acid synthesis pathway, as described in the reference, is key to creating saturated fatty acids, which can then be modified in some organisms (like plants) to produce the essential unsaturated fatty acids. The reference states that the fatty acid synthase (FAS) enzyme complex produces fatty acids following the synthesis of malonyl-CoA. This complex, which includes the acyl carrier protein (ACP), links the enzymes needed for the process. This base process creates fatty acids which plants can modify into essential fatty acids, which is where the essence of the answer to this question lies.
Here's how we can put it all together:
- General Fatty Acid Synthesis: All organisms (including plants, animals, and bacteria) can synthesize saturated fatty acids from acetyl-CoA, using the FAS complex.
- Unsaturation by Plants: Plants have additional enzymes (desaturases) that can introduce double bonds into these saturated fatty acids. This is how they create ALA and LA.
- Dietary Acquisition for Humans: Humans lack these desaturases, so we must obtain ALA and LA from plant-based foods (or from animals that have consumed plant-based foods).
Therefore, biosynthesis of essential fatty acids specifically refers to the pathways in plants and other organisms (not humans) that produce ALA and LA using desaturases to modify saturated fatty acids.
