What is arachidonic acid definition synthesis functions and health effects
Arachidonic Acid is an important fatty acid and aids with the biosynthesis of thromboxanes and prostaglandins. It is an unsaturated and essential fatty acid present in the human body. It is usually present in human and animal fat as well as in the brain and glandular organs.
Arachidonic Acid is also an important constituent of animal phosphatides. It is developed by the synthesis of dietary linoleic acid. It is a long-chain fatty acid that contains four double bonds at positions 5, 8, 11 and 14. It plays a crucial role in the human body as a metabolite.
Many experts also call it a polyunsaturated fatty acid covalently bound in the esterified form in cell membranes. After certain irritations or injuries, our body releases Arachidonic Acid. It is oxygenated by the enzyme systems, which lead to the formation of a vital group of inflammatory mediators called the eicosanoids.
Arachidonic acid is derived from the Latin word Arachis, which means peanuts. Unlike what its name suggests, this fatty acid is not present in higher amounts in peanuts. Arachidonic acid is rarely found in plants and is mostly produced in animal bodies.
Arachidonic Acid Function
The arachidonic acid function is important to understand if you want to know about its overall role. The arachidonic acid comprises 20 carbons with four double bonds. To be precise, it is available in optimum quantities in foods of animal origin. For instance, arachidonic acid is available abundantly in dairy products and meat.
In human beings, arachidonic acid is usually synthesised by the saturation and elongation of linoleic acid. Linoleic acid is an essential fatty acid present in the human body. The arachidonic acid function is mainly present in cellular membranes. Note that the arachidonic acid pathway depends heavily on linoleic acid. In simple words, a lack of linoleic acid can hinder the processes related to arachidonic acid.
It is important here to note that the endogenous metabolism of phospholipases is a good way to produce arachidonic acid. Thus, both the exogenous and endogenous processes can be used as substrates. The arachidonic acid pathway is mainly prominent in the cellular membranes of the human body.
The significance of lipids in cellular organisation and signalling is gaining increasing momentum. This puts complex lipids and fatty acids like arachidonic acid at the forefront of biomedical research. In phospholipids, the most important fatty acid present is the arachidonic acid.
It plays a crucial role in the cellular structure. Hence, the arachidonic acid pathway is pretty prominent in the cellular structures of animals. With its four double bonds, the arachidonic acid enables our cellular membranes to be flexible. And as we all know, flexibility is an essential parameter for the proper functioning of the cells. Arachidonic acid ensures that the cells present in our skeletal, immune and nervous systems function to their fullest potential.
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The Arachidonic Acid Metabolism
To be precise, the arachidonic acid metabolism facilitates a pathway for the production of short-lived and fast-acting signalling molecules. In case you don’t know, systolic phospholipase releases arachidonic acid from the phospholipid pool in cellular membranes.
After their liberation, the various types of oxygenases can act on the arachidonate to provide a single or two atoms of oxygen. Arachidonic acid metabolism is pretty important for the human body to maintain its overall cell structures.
Arachidonic Acid and Inflammation
It is important to know about the arachidonic acid structure to be aware of its role during inflammation. To be precise, the arachidonic acid structure comprises various chains of carbon. Note that arachidonic acid is a carboxylic acid with a twenty carbon chain and four double bonds.
Moreover, the first double bond is situated at the sixth carbon from the omega end. The skeletal muscle of the human body is an active site of arachidonic acid. Apart from being involved in cellular signalling, the arachidonic acid structure also highlights that it acts as a lipid second messenger.
Conclusion
As you can see, arachidonic acid is an important inflammatory intermediate and also acts as a vasodilator. The four double bonds present in the arachidonic acid makes it vulnerable to oxidation from which the eicosanoids are produced. One of the main arachidonic acid benefits is that the eicosanoids produced from arachidonic act as the regulators of inflammation.
FAQs on Arachidonic Acid Structure Functions and Biological Role
1. What is arachidonic acid?
Arachidonic acid is a polyunsaturated omega-6 fatty acid with the molecular formula C20H32O2 and four cis double bonds. It is a 20-carbon carboxylic acid classified as a 20:4 (ω-6) fatty acid, meaning it has 20 carbons and 4 double bonds. In chemical terms, it contains a terminal –COOH (carboxyl) group and multiple C=C double bonds that influence its reactivity and biological function.
2. What is the chemical structure of arachidonic acid?
The chemical structure of arachidonic acid is a 20-carbon chain with four cis double bonds at Δ5, Δ8, Δ11, and Δ14 positions. Its systematic IUPAC name is (5Z,8Z,11Z,14Z)-eicosa-5,8,11,14-tetraenoic acid. Key structural features include:
- A terminal carboxyl group (–COOH)
- Four cis (Z) double bonds
- A long hydrophobic hydrocarbon chain
3. Is arachidonic acid saturated or unsaturated?
Arachidonic acid is a polyunsaturated fatty acid (PUFA) because it contains four carbon–carbon double bonds. Saturated fatty acids have no double bonds, while unsaturated fatty acids have one or more. Since arachidonic acid has four C=C bonds, it is classified as highly unsaturated and specifically as an omega-6 fatty acid.
4. What is the difference between arachidonic acid and linoleic acid?
The main difference is that arachidonic acid has 20 carbons and 4 double bonds, while linoleic acid has 18 carbons and 2 double bonds.
- Arachidonic acid: C20H32O2, 20:4 (ω-6)
- Linoleic acid: C18H32O2, 18:2 (ω-6)
5. How is arachidonic acid formed in the body?
Arachidonic acid is formed from linoleic acid through enzymatic desaturation and elongation reactions. The process involves:
- Δ6-desaturation of linoleic acid (18:2)
- Chain elongation to 20 carbons
- Δ5-desaturation to form arachidonic acid (20:4)
6. What is the role of arachidonic acid in cell membranes?
Arachidonic acid is a key component of membrane phospholipids, where it helps regulate membrane fluidity and signaling. It is esterified at the sn-2 position of phospholipids and can be released by the enzyme phospholipase A2. Its multiple double bonds increase membrane flexibility and serve as precursors for signaling molecules.
7. What are eicosanoids derived from arachidonic acid?
Eicosanoids are signaling molecules formed from arachidonic acid through oxidation pathways. Major types include:
- Prostaglandins
- Thromboxanes
- Leukotrienes
8. What is the molar mass of arachidonic acid?
The molar mass of arachidonic acid (C20H32O2) is approximately 304.47 g·mol-1. This is calculated using atomic masses:
- 20 × 12.01 g·mol-1 (C)
- 32 × 1.008 g·mol-1 (H)
- 2 × 16.00 g·mol-1 (O)
9. Why is arachidonic acid called an omega-6 fatty acid?
Arachidonic acid is called an omega-6 fatty acid because its first double bond is located at the sixth carbon from the methyl (ω) end. In omega notation, counting starts from the terminal CH3 group rather than the carboxyl carbon. Since the first C=C bond appears at position 6, it belongs to the omega-6 family.
10. What chemical reactions does arachidonic acid undergo?
Arachidonic acid undergoes oxidation, esterification, and hydrogenation reactions due to its carboxyl group and multiple double bonds. Common reactions include:
- Oxidation by COX and LOX enzymes to form eicosanoids
- Esterification with glycerol to form phospholipids
- Hydrogenation of C=C bonds under catalytic conditions
