The main difference between beta-oxidation and fatty acid synthesis is that beta oxidation breaks down fatty acids into acetyl CoA. In contrast, fatty acid synthesis synthesizes fatty acids from acetyl CoA.
Beta oxidation and fatty acid synthesis are two metabolic processes of acetyl CoA. They are essential in fatty acid metabolism.
Key Areas Covered
1. What is Beta Oxidation
– Definition, Facts, Reactions
2. What is Fatty Acid Synthesis
– Definition, Facts, Reactions
3. Similarities Between Beta Oxidation and Fatty Acid Synthesis
– Outline of Common Features
4. Difference Between Beta Oxidation and Fatty Acid Synthesis
– Comparison of Key Differences
Key Terms
Beta Oxidation, Fatty Acid Synthesis
What is Beta Oxidation
Beta oxidation is a type of fatty acid oxidation that occurs in the mitochondria and peroxisomes in eukaryotes. It is a significant source of metabolic energy during inter-prandial periods and in high energy-demand processes such as exercise. The two hormones, epinephrine and glucagon, induce lipolysis, releasing fatty acids. Beta oxidation provides energy for skeletal muscle, heart muscle, and kidneys in the scarcity of glycogen. Further, mitochondrial beta-oxidation occurs in two ways. In the heart and skeletal muscles, beta-oxidation in mitochondria produces substrates for the TCA cycle, which is acetyl CoA. It provides energy for skeletal and heart muscles.
Figure 1: Beta Oxidation
Furthermore, beta-oxidation in hepatocytes produces acetyl CoA that involves in the ketone body synthesis during prolonged fasting conditions. Beta-oxidation yields four ATP in the form of two FADH and 1 NADH. Peroxisomal beta-oxidation is significant in metabolizing very-ling chain fatty acids composed of 24-26 carbon units.
In peroxisomes, another type of fatty acid oxidation occurs, known as alpha oxidation which degrades the by-products of chlorophyll. The third type of fatty acid oxidation occurs in the endoplasmic reticulum, processing large, water-insoluble fatty acids that are toxic to the cells in higher concentrations.
What is Fatty Acid Synthesis
Fatty acid synthesis is the metabolic process that synthesizes fatty acids from acetyl CoA and NADPH by the enzyme fatty acid synthase. It occurs in the cytoplasm of the cell. Most fatty acids are derived from carbohydrates via the glycolytic pathway. Three fatty acids combine with glycerol by ester bonds to form triglycerides in fatty acid synthesis. Triglyceride is the final product of the lipogenic process.
Figure 2: Straight Chain Fatty Acid Synthesis
Moreover, a phospholipid is formed by combining two fatty acids with an alcohol group that is phosphorylated. It includes the bulk of the lipid bilayers that form the cell membrane. The cell membrane also surrounds the organelles, including the nucleus, endoplasmic reticulum, mitochondria, and Golgi apparatus.
There are two types of straight-chain fatty acids. They are saturated fatty acids and unsaturated fatty acids. Fatty acid synthase II is the enzyme responsible for forming straight-chain fatty acids. It occurs in both mitochondria and prokaryotes. In animals and fungi, fatty acid synthase I is the enzyme responsible for forming straight-chain fatty acids. Another process of fatty acid synthesis is the conversion of carbohydrates into fatty acids. This process occurs in the liver, adipose tissue, and mammary glands. Pyruvate is the intermediate of the transformation of carbohydrates into fatty acids. Here, mitochondria convert pyruvate into acetyl CoA. This acetyl CoA is transported to the cytosol to synthesize fatty acids.
Similarities Between Beta Oxidation and Fatty Acid Synthesis
- Beta oxidation and fatty acid synthesis are two metabolic processes of fatty acids.
- Fatty acids are an essential constituent in lipids.
Difference Between Beta Oxidation and Fatty Acid Synthesis
Definition
Beta oxidation is a metabolic process with multiple steps in which fatty acid molecules are broken down to produce energy. In contrast, fatty acid synthesis refers to a series of steps through which fatty acids are produced from acetyl CoA.
Type of Process
Beta oxidation is the breaking down of fatty acids into acetyl CoA, while fatty acid synthesis is the formation of fatty acids from acetyl CoA.
Type of Metabolic Process
Beta oxidation is a catabolic process, while fatty acid synthesis is an anabolic process.
Enzymes
Several enzymes involve in breaking fatty acids into acetyl CoA, while fatty acid synthase is the enzyme involved in the fatty acid synthesis.
Occurrence
Beta oxidation occurs in the cytoplasm of prokaryotes and mitochondria in eukaryotes, while fatty acid synthesis occurs in the cytoplasm in both prokaryotes and eukaryotes.
ATP
Beta oxidation produces ATP, while fatty acid synthesis uses ATP.
Reductants
Beta oxidation uses NADH and FADH as reductants, while fatty acid synthesis uses NADPH as a reductant.
Energy
Beta oxidation releases energy, while fatty acid synthesis uses energy.
Conclusion
In brief, beta-oxidation and fatty acid synthesis are two metabolic processes of fatty acids. Beta oxidation is the breaking down of fatty acids into acetyl CoA. It is a catabolic process. It occurs in the cytoplasm of prokaryotes and mitochondria in eukaryotes. Also, it produces ATP and uses NADH and FADH as reductants. In comparison, fatty acid synthesis is an anabolic process in the cytoplasm of both prokaryotes and eukaryotes. It uses energy, and NADPH is the type of reductant used in fatty acid synthesis. Therefore, the main difference between beta-oxidation and fatty acid synthesis is the type of metabolic process.
References:
- Talley JT, Mohiuddin SS. Biochemistry, Fatty Acid Oxidation. [Updated 2023 Jan 16]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-
- Fatty acid synthesis. Fatty Acid Synthesis – an overview | ScienceDirect Topics.
Image Courtesy:
- “LCHAD deficiency” By User:Innerstream – Own work (Public Domain) via Commons Wikimedia
- “Saturated Fatty Acid Synthesis” By Hbf878.- Own Work (CC0) via Commons Wikimedia
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