Fatty acid synthesis

Definition

Fatty acid synthesis is the metabolic process by which cells create fatty acids from acetyl-CoA and malonyl-CoA, primarily occurring in the liver and adipose tissue. This process is essential for producing long-chain fatty acids that serve as energy storage molecules and building blocks for complex lipids. Fatty acid synthesis is closely linked to lipid metabolism, particularly how the body utilizes and stores fats, and is influenced by hormonal signals that regulate energy balance and substrate availability.

5 Must Know Facts For Your Next Test

1. Fatty acid synthesis occurs in the cytoplasm of cells and involves the enzyme fatty acid synthase, which catalyzes the condensation reactions needed to build fatty acids.
2. The process starts with acetyl-CoA being carboxylated to form malonyl-CoA, which then provides two-carbon units for elongating the growing fatty acid chain.
3. Insulin stimulates fatty acid synthesis by promoting the expression of key enzymes involved in this pathway, while glucagon and epinephrine inhibit it during periods of fasting or stress.
4. NADPH, generated mainly from the pentose phosphate pathway, is required as a reducing agent during fatty acid synthesis to reduce the growing fatty acid chain.
5. Long-chain fatty acids synthesized through this process are important for forming triglycerides and phospholipids, which are essential components of cell membranes and energy storage.

Review Questions

• How does insulin influence fatty acid synthesis and what are the implications for energy storage in the body?
  • Insulin plays a crucial role in stimulating fatty acid synthesis by enhancing the expression of enzymes like acetyl-CoA carboxylase. This leads to an increase in malonyl-CoA levels, promoting the conversion of excess glucose into fatty acids for storage as triglycerides. The implication is that during periods of high glucose availability, such as after meals, insulin encourages energy storage in adipose tissues while decreasing the mobilization of stored fats.
• Discuss the role of acetyl-CoA and malonyl-CoA in the process of fatty acid synthesis and how their availability affects this pathway.
  • Acetyl-CoA serves as the starting point for fatty acid synthesis, while malonyl-CoA acts as a donor of two-carbon units necessary for elongation. The availability of these substrates is critical; when excess carbohydrates are consumed, more acetyl-CoA is produced through glycolysis, increasing malonyl-CoA production. This drives fatty acid synthesis forward. Conversely, during fasting states when energy substrates are limited, levels of these compounds decrease, inhibiting fatty acid synthesis and promoting beta-oxidation instead.
• Evaluate the interconnectedness of fatty acid synthesis with lipid metabolism processes such as beta-oxidation and ketone body formation.
  • Fatty acid synthesis and beta-oxidation are interconnected pathways that manage energy homeostasis. While fatty acid synthesis creates energy storage forms from excess substrates under anabolic conditions (like high carbohydrate intake), beta-oxidation breaks down stored fats for energy when glucose is scarce. Additionally, when fatty acids undergo incomplete oxidation, they can lead to ketone body formation during prolonged fasting or low carbohydrate intake. This highlights how these processes are balanced based on nutrient availability and hormonal signals to maintain metabolic equilibrium.

Related terms

Acetyl-CoA: A central metabolic intermediate that plays a crucial role in the synthesis of fatty acids and serves as a substrate for energy production in the citric acid cycle.

Malonyl-CoA: A three-carbon molecule derived from acetyl-CoA, crucial for fatty acid synthesis as it provides the carbon units needed for chain elongation.

Fatty Acid Desaturation: The process of introducing double bonds into saturated fatty acids, which alters their physical properties and function, often regulated by enzymes that respond to metabolic needs.