Lipid Peroxidation: Definition and Types

Lipids are compounds that are organic in nature. Furthermore, they are insoluble in water. The human body synthesizes lipids in the liver. Butter, cheese, ghee oil, and whole milk are the sources that are rich in lipids. Lipid peroxidation is a process that is metabolic in nature and causes oxidative deterioration of the lipids. This deterioration of lipid is caused due to its reaction with oxygen-related elements. 

Also Read: Difference between Lipids and Fats

Key Terms: Lipids, Lipid Peroxidation, Simple lipids, Complex lipids, Lipid Emulsion

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What are Lipids?

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Lipids are organic compounds that are insoluble in water. They are identified as fatty acids that are soluble in fats, grease oils, and other such nonpolar solvents. Hence, lipids molecules are nonpolar in nature. Butter, cheese, ghee oil and whole milk are significant sources of lipids. Essentially, lipids are molecules that are made of hydrocarbons. Lipids are also called the structural and functional building blocks of living cells.

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Types of Lipids

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Lipids are classified into two types based on their structural complexities: Simple Lipids and Complex Lipids. Following are the brief explanations of both:

Simple Lipids 

Simple lipids are either free in nature or combined with alcohol. Furthermore, the combination of alcohol takes place due to the ester linkage. These types of lipids are long-chain fatty acids that are present in triacylglycerol (TAG) and wax esters.

TAGs are the molecules that are non-polar in nature. They are non-polar due to unavailability of free polar molecules. When seen under the microscope, TAGs appear as oil droplets in aqueous cytosol.

Waxes are also a type of simple lipids and they are considered to be the simplest fatty acid esters. In fact, waxes are the energy sources in the planktons. The melting point of the waxes is higher than TAGs.

Simple Lipids

Complex Lipids 

Complex lipids are lipids that include three or more chemical elements. These elements can consist of glycerol, fatty acids, sugar, one log chain base, etc. Complex lipids are polar in the property.

In fact, complex lipids are of different types. They are: Phospholipids. Glycolipids, Sulpholipids and Lipoproteins. As per definitions of complex lipids, these different types of complex lipids constitute lipids in mixture with the other substances as well.

Phospholipids are mixture of lipid, phosphoric acid and nitrogenous base. Glycolipids are formed by the mixture of lipid and carbohydrate. Sulpholipids are formed by mixture of lipid and sulphur. Lipoproteins are formed by mixture of lipid and protein. 

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Lipid Peroxidation

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Lipid peroxidation happens when there is an oxidative deterioration of the lipids. Furthermore, this process occurs due to the reaction of lipids with oxygen-related elements. Lipid peroxidation is an essential process that happens not only in animals but also in plants.

The process of lipid peroxidation involves three stages: Initiation, Propagation, and Termination. Following is the explanation of all the three processes:

Initiation

This stage involves producing fatty acid radicals when a hydrogen atom is combined with a reactive oxygen species such as hydroxyl radicals.

The compounds belonging to the reactive oxygen family are the most used initiators in this stage of liquid peroxidation. Reactive oxygen species like Hydroxides (OH) and Hydrogen superoxide (OOH) are some of the examples of the initiators. Furthermore, it is the ability of these species to combine with Hydrogen atoms to form water and radical fatty acids, due to which they are used as initiators.

Also Read: Amino Acid

Propagation

In this stage, the fatty acids that are free and unstable react with the oxygen of molecular state to form the radicals of peroxyl-fatty acid.

Propagation also results in the formation of materials that are acid-reactive and lipid hydroperoxides.

The radicals created in the propagation stage are very unstable species and reactive with other free fatty acids thereby, producing different species of fatty radical acids. This is a very long-running cycle as the newly formed fatty radical acid further reacts in the same way.

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Termination 

Termination is the process in which the lipid peroxyl radicals react with other such similar radicals to form non-radical products. In this stage, the chain reaction of the peroxyl-fatty acid ends and gets terminated.

Termination happens successfully only when the radical species have high concentration of free molecules. This increases the probability of collision of the radical acid molecules. When this happen all the radical and free molecules get combined following which there are no free radical molecules. Due to this, the process of lipid peroxidation ends. 

Lipid Peroxidation

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Lipid Peroxidation in Medical Science

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Lipid peroxidation finds its significance in the field of medical sciences. It helps wear off the tissues that cause inflammatory diseases, angina problems, strokes, cancer, atherosclerosis, and the aging process in human beings.

Lipids essentially are the energy providers that also facilitate the production of important hormones in our body. Lipids find their importance in the digestion and absorption of food.

Polyunsaturated Fatty Acid (PUFAs) is a form of lipid peroxide that is essential for the proper functioning of retina and brain. They also find importance in their roles as antioxidants, immune-regulators and anti-cancer factors.

Lipid peroxide has the ability to immobilize enzymes, destroy proteins and phospholipid structure like cell membranes that lead to their dysfunction. 

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Things to Remember

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• Lipids are compounds that are organic in nature. Furthermore, they are insoluble in water.
• The human body synthesizes lipids in the liver. Butter, cheese, ghee oil, and whole milk are the sources that are rich in lipids.
• Lipids essentially are the energy providers that also facilitate the production of important hormones in our body.
• Lipid peroxidation happens when there is an oxidative deterioration of the lipids.
• Process of lipid peroxidation involves three stages: Initiation, Propagation, and Termination.

Also Read: Macromolecule