Fatty acid synthesis

Definition

Fatty acid synthesis is the metabolic process through which organisms create fatty acids from acetyl-CoA and malonyl-CoA, using a series of enzymatic reactions. This process plays a critical role in energy storage, membrane formation, and signaling molecules, linking directly to broader metabolic pathways including anaplerotic reactions and the pentose phosphate pathway, which provide necessary substrates and reducing equivalents for synthesis.

5 Must Know Facts For Your Next Test

1. Fatty acid synthesis primarily occurs in the cytosol of liver and adipose tissue cells, where enzymes such as fatty acid synthase are localized.
2. The process involves repeated cycles of condensation, reduction, dehydration, and reduction, ultimately elongating the fatty acid chain.
3. NADPH is crucial in fatty acid synthesis, as it provides the reducing power needed for the conversion of ketoacyl intermediates into fatty acids.
4. The pentose phosphate pathway not only generates NADPH but also produces ribose-5-phosphate for nucleotide synthesis, linking nucleic acid metabolism with lipid metabolism.
5. Regulation of fatty acid synthesis is tightly controlled by hormonal signals such as insulin, which promotes the process when energy is abundant.

Review Questions

• How does acetyl-CoA contribute to the process of fatty acid synthesis?
  • Acetyl-CoA acts as the primary substrate for fatty acid synthesis, providing the initial two-carbon unit that forms the backbone of the fatty acid chain. During this process, acetyl-CoA is converted into malonyl-CoA through carboxylation, which then serves as a two-carbon donor in the elongation cycles catalyzed by fatty acid synthase. Thus, acetyl-CoA is essential for both initiating and sustaining the fatty acid synthesis pathway.
• Discuss the role of NADPH in fatty acid synthesis and how it is produced through other metabolic pathways.
  • NADPH plays a critical role as a reducing agent in fatty acid synthesis, providing the necessary electrons for reducing ketoacyl intermediates to form long-chain fatty acids. It is primarily generated via the pentose phosphate pathway, where glucose-6-phosphate is oxidized to produce NADPH while also yielding ribose-5-phosphate. This connection illustrates how carbohydrate metabolism supports lipid biosynthesis by supplying NADPH needed for anabolic processes like fatty acid synthesis.
• Evaluate the regulatory mechanisms involved in fatty acid synthesis and their implications on metabolic health.
  • Fatty acid synthesis is regulated by various hormonal signals, particularly insulin, which enhances lipogenesis when energy levels are high. Conversely, glucagon and epinephrine inhibit this process during fasting or energy deficit. This regulatory interplay ensures that fatty acids are synthesized when there is excess glucose and energy available while preventing unnecessary storage during energy scarcity. Disruption of these regulatory mechanisms can lead to metabolic disorders such as obesity and diabetes, emphasizing their importance in maintaining metabolic homeostasis.

Related terms

Acetyl-CoA: A central metabolite that serves as a key building block in various biochemical pathways, including fatty acid synthesis, where it is the primary substrate.

NADPH: A reducing agent generated primarily by the pentose phosphate pathway that provides the necessary electrons for biosynthetic reactions, including fatty acid synthesis.

Malonyl-CoA: An intermediate in fatty acid synthesis that is formed from acetyl-CoA and bicarbonate and acts as a two-carbon donor in the elongation of fatty acids.