Lipids

Introduction

We need food to stay alive. Food gives us the energy to work, run and play. In addition, it 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. The amount of each of these components depends upon the age and physical activity of a person.

Lipids are hydrocarbon molecules. Lipids form the building framework of the structure and function of cells of living organisms. Lipids, due to their nonpolar nature, are insoluble in water. The food rich in lipids includes oil, butter, cheese, fried food, etc. Lipids are synthesized in the liver.

Properties of Lipids

The properties of lipids are as follows −

• It is a nonpolar molecule and insoluble in water and soluble in chloroform.

• Lipids are energy-rich molecules and provide energy to the body.

• It is mainly composed of a hydrocarbon chain.

• It may either be liquid or amorphous solid at room temperature.

• Saturated fatty acids have a melting temperature above 27⁰C.

• The hydrocarbon which is part of the fatty acid molecule is resistant to chemical attack unless a double bond carbon-carbon is present.

Structure

The polymers of fatty acids are known as lipids. It is a straight long chain of hydrocarbons and has a small polar region containing oxygen. The lipid structure is described as saturated and unsaturated fatty acid.

• Saturated fatty acids − These fatty acids are not branched and it's a linear chain of CH₂ groups linked by a single bond of carbon-carbon. The carboxylic acid group is present in the terminal end of the carbon molecule.

• Unsaturated fatty acids − In this type of fatty acid, one or more carbon-carbon double bonds are present. The term unsaturated indicates a maximum number of hydrogen atoms bonded to each carbon in the molecule.

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Classification

The lipids are classified as saponifiable lipids and nonsaponifiable lipids.

• Saponifiable lipids − One more ester group constitutes saponifiable lipids. It undergoes hydrolysis in the presence of enzymes, acid, or base. Further, it is divided into polar and nonpolar lipids. Triglycerides and sphingolipids are examples of nonpolar and polar lipids, respectively.

• Nonsaponifiable lipids − These lipids do not contain the ester group. Terpenes and steroids are examples of nonsaponifiable lipids.

Types of Lipids

Three different types of lipids are described below −

Simple Lipids

• Fats − It is the ester of fatty acids with glycerols.

• Waxes − It is the ester of fatty acids with a higher molecular weight of alcohol.

Complex Lipids

• 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.

Functions of Lipids

Lipid plays an important function in our body that can be described below −

• Lipids act as a chemical messenger. The esterified form of lipids works as signaling lipids that carry messages to other cells. They are inactive till they reach their target cells and also sometimes they bind to proteins.

• Triglycerides are known as storage lipids. Lipids are energy-rich molecules and provide energy to the body.

• It helps in maintaining temperature. The layers of fats that are present under the skin help in insulation and protection from the cold.

• It functions as a structural component of the body.

• It furnishes hydrophobic barricades that separate subcellular substances from aqueous contents that are present in the cell body.

• Certain types of lipids work as hormones.

• Activators of enzymes e.g., glucose-6-phosphatase β-hydroxybutyric dehydrogenase (a mitochondrial enzyme) etc., require phosphatidylcholine micelles for activation.

Examples

• Transfat − It is a dietary fat and is prepared by cooking vegetable oils in the presence of hydrogen. The hydrogen is used as a catalyst and this process is known as hydrogenation. Trans fats are not good for health and are the worst type of fats.

• Omega fatty acids − It is an integral part of the cell membrane throughout the body. It helps in hormone production and regulates blood clotting and inflammation. Apart from these omega fatty acids help in the prevention of heart disease, stroke, arthritis, rheumatism, etc. The food that is rich in omega fatty acids is fish, wall-nuts, flax seeds, vegetable oils, flaxseeds oil, and leafy vegetables.

• Waxes − They are esters that are formed from the long chain of carboxylic acids and alcohols. Most of the plant's leaves and fruits contain a waxy coating that prevents them from small predators as well as from dehydration. The animals that bear furs and birds' feathers possess a waxy coating.

• Phospholipids − The phospholipids can be synthesized by the body itself and form an outermost protective membrane around the cell. It contains a phosphate group and is found in both plants and animals.

• Steroids − Steroids are hydrophobic and not soluble in water hence it is considered a type of lipid. It is a kind of hormone produced by the adrenal gland.

• Cholesterol − 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.

Conclusion

Lipids are hydrocarbon molecules. Lipids, due to their nonpolar nature, are insoluble in water. Food rich in lipids includes oil, butter, cheese, fried food, etc. Lipids are synthesized in the liver. The different types of lipids that are present have similar properties like insoluble in water. Lipids plays an important function in our body.

FAQs

Q1. Why our body needs cholesterol?

Ans. Cholesterol is the main sterol of animals. Our body needs cholesterol to build healthy cells. But high levels of cholesterol may lead to cardiac-related diseases.

Q2. Why the trans fats are harmful to health?

Ans. Trans-fat is considered harmful to health as it creates an adverse effect on the heart, blood vessels, and the rest of the body. It also increases the parameter of the liver.

Q3. What do you understand by ester groups?

Ans. An ester is a group of chemical compounds. This group is constituted by the binding of the alcohol group with a group of organic acids by the loss of water molecules.

Q4. What are simple lipids?

Ans. A simple lipid constitutes fatty acids that contain only the group of alcohol. It is insoluble in water but soluble in nonpolar organic solvents like chloroform.

Q5. What is fat?

Ans. Fat is a type of lipid and oily substance present under the skin of adipose tissue. They are solid and give energy to us.