Lipid Peroxidation

Introduction to Lipids

The nutrients that are present in the food give us the energy to work, run and play. In addition, protects us from diseases, heals our wounds, and keeps us healthy. There are five components of food that are essential and they are carbohydrates, fats, protein, vitamins, and minerals. Fat is a type of lipid and oily substance present under the skin in adipose tissue. They are broken down to obtain energy. Lipids are hydrocarbon molecules. Lipids form the building framework of the structure and function of cells of living organisms. Due to the nonpolar nature, lipids are insoluble in water. The food rich in lipids includes oil, butter, cheese, fried food, etc. Lipids are synthesized in the liver. Organisms use lipids to store energy.

Types of Lipids

Three different types of lipids are described below −

• Triglycerides −Out of the three forms of lipids, triglycerides are the main form of lipids. Normally in the diet, approximately 95% of lipids are present in the form of triglycerides. They can be solid and liquid at room temperature.

• Phosopholipids − This is found in both plants and animals. The phospholipids can be synthesized by the body itself and form an outermost protective membrane around the cell.

• Sterols − Sterols are complex molecules that contain interlinking rings of the carbon atom. Carbon, hydrogen, and oxygen are attached to the side chain. Cholesterol is one of the best-known sterols.

Significance

The significance of lipids is as listed below −

• It forms a protective covering for fruits leaves in plants and feathers, fur, etc., in animals.

• The food that is surplus gets converted and stored as lipids.

• The fats are deposited in some vital organs in the body and provide protection against mechanical energy and pressure.

• The fats work as a heat insulator in some mammals like whales, blubber, etc.

• Steroids controls many physiological functions.

Lipid Peroxidation

Lipid peroxidation is a chain of oxidative reactions. It takes place for glycolipids, cholesterol, unsaturated fatty acids, and its esters. In this process, the breakdown of lipid molecules that constitute carbon double bonds or multiple bonds occurs. The peroxide radicals right away react with peroxide radicals and stop the chain reactions. The lipid molecule breaks down to produce unpleasant taste and foul-smelling products at high temperatures. Epoxides, ketones, acids, and aldehydes are examples of these products.

Steps of Lipid Peroxidation

The mechanism of lipid peroxidation involves three steps that are described below −

• Initiation − This is the first step that generates free radicals in fatty acids. Here the initiators are reactive oxygen species like oxygen or OH. In an unsaturated fatty acid, these initiators combine with hydrogen to form a free radical (R).

• Propagation − A radical that is produced in the initiation stage reacts with a nonradicle to form a new one. It is a long chain reaction as the radicles should reach their maximum concentration level. High radical concentration may provide by the environment that has high chance for the formation of non-radical species. This can be done by a combination of two radicals. Then, termination of the lipid oxidation is reached.

• Termination − Living organisms have different molecules that speed up termination by neutralizing free radicals. Thereby they protect the cell membrane. Antioxidants such as vitamin C and vitamin E may inhibit lipid peroxidation.

Hazards of Lipid Peroxidation

The hazards of lipid peroxidation are listed below −

• The biological membrane consists mainly of lipids. This membrane can be impaired if the termination is not done quickly.

• The end product of lipid peroxidation may be cancerous in addition to this it is responsible for diabetes, premature birth disorders, organ injury, atherosclerosis, aging, Parkinson's disease, etc.

• Lipid peroxidation is able to inactive sensitive protein.

• Alzheimer’s disease is a neurodegenerative disease characterized by lipid peroxidation.

Diagnosis Test

The different diagnostic tests of lipid peroxidation are as follows −

• Conjugated dienes − This method is used to determine nonspecific lipid peroxidation. Lipid peroxidation is mainly caused by the radicals that are present in biological samples.

• TBARS − TBARS (Thiobarbituric Acid Reactive Substance) is a widely used method to determine lipid peroxidation. It is very popular due to its simplicity and cost-effectiveness. It is based on the potentiality of malondialdehyde to react with thiobarbituric acids.

• Iodometric method − It is also the oldest method and is still used in the determination of lipid peroxide numbers. This method is based on the potential of lipid hydroperoxide to oxidize iodide to iodine.

Importance of Lipid Peroxidation

• Lipid peroxidation plays a crucial role in the health of human beings.

• They perform as signaling intermediates in modulating the physiological functions of cells.

Significance of Lipid Peroxidation

• Lipid peroxidation is responsible for several diseases like diabetes, atherosclerosis, ischemia-reperfusion injury, and rheumatoid arthritis.

• At the time of lipid peroxidation, lipoxidation products are formed by chemical reactions that alter amino acids in proteins. They can work as stress oxidative indicators in vitro.

• In the course of lipid peroxidation reactions blend of aldehydes is generated. This aldehyde reacts with nucleophilic groups in proteins to form Schiff base or Michael addition compounds.

• The cell membrane becomes porous due to lipid peroxidation chain reaction.

• Due to this radioactive substance can make an entry through the porous cell membrane and reacts with the nucleus. That may lead to the disintegration of the nucleus which may be permanent.

• As a consequence of lipid peroxidation, the cell membrane may be partially spoiled which can slow down or stop crucial processes of life as well as restrict the exchange of minerals.

Conclusion

Lipids are the structural and functional framework of cells in living organisms. Lipids are insoluble in water due to their nonpolar nature. And are further classified into triglycerides, phospholipids, and sterols. Out of these types, triglycerides are the most common lipids. Lipid peroxidation is a chain of oxidative reactions. It takes place in glycolipids, cholesterol, unsaturated fatty acids, and its esters.

FAQs

Q1. What is Parkinson's disease?

Ans. Parkinson’s disease is caused due to disorder of the central nervous system. The symptoms include inflexibility, trembling, and unable to make the body balance and coordinate.

Q2. What is an antioxidant?

Ans. Antioxidants are of two types: naturally occurring and man-made. Their main function is to prevent or slow down some types of cell damage. Some of the fruits and vegetables are rich in antioxidants.

Q3. What is atherosclerosis?

Ans. Atherosclerosis is the pile of fats, cholesterol, and other substances in the wall of the artery. These substances make the path of the artery narrow thereby blood flow to the heart is interrupted. That further leads to blood clot and even heart attack.

Q4. What is a radical?

Ans. Radical can be an atom, molecule, or ion. It consists at least one unpaired valence electron. The Hydroxyl group is an example of a radicle.

Q5. What is cholesterol?

Ans. Cholesterol is a wax-like substance and one of the important lipids found in the cell membrane. It is found in different sources of food. The various types of cholesterol found in the blood cells are triglycerides, LDL, HDL, VLDL.