In biology and biochemistry, Lipids are made up of carbon, hydrogen, and oxygen atoms, and occasionally they also include phosphorus, nitrogen, sulphur, and other elements.

Due to their significant metabolic and nutritional roles, cholesterol and other fatty acids are the most typical molecules in this area. Fats and oils are the main exponents of lipids present in diets and in nutritional processes.

A lipid is a biomolecule that is a fatty acid and its derivatives are a class of chemical molecules that share the property of being insoluble in water but soluble in organic solvents. Multiple oils, waxes, and steroids found in nature are among them.

Introduction to “Lipids”

• Lipids are organic non-polar molecules.
• According to the general rule of solubility, “like dissolves like,” they are soluble in ether, benzene, and hexane (non-polar solvents) but insoluble in water due to the non-polar nature of water.
• Lipids are therefore non-polar compounds, which is why they are soluble in non-polar solvents (ether, benzene etc.).

Examples of lipids that can be found in both plants and animals include:

Lipids include:

• Fats and oils (non-polar in nature, soluble in a non-polar solvent and insoluble in water)
• Cholesterol (non-polar in nature, soluble in a non-polar solvent and insoluble in water)
• Sex hormone (non-polar in nature, soluble in a non-polar solvent and insoluble in water)
• Phospholipids (non-polar in nature, soluble in a non-polar solvent and insoluble in water)
• Vitamin-A, Vitamin-D, Vitamin-E and Vitamin-K (non-polar in nature, soluble in a non-polar solvent and insoluble in water)

Fat:

At room temperature, a solid lipid is referred as fat.

Oil:

At room temperature, a liquid lipid is referred as oil.

Fatty acids:

• Long-chain carboxylic acids make up fatty acids.
• They serve as the foundation for lipids.
• Simple lipids, commonly known as fatty acids, are what makeup fat and oil.
• Because they are esters of fatty acids and contain tri-hydroxy alcohol and glycerol, fat and oil are sometimes known as glyceryl esters or glycerides.
• Animal fat contains the (fatty acid) stearic acid, C₁₇H₃₅COOH.
• The following list of common fatty acids includes their condensed formulas:

Name of Fatty Acid	Condensed Structural Formula	Source of Fatty Acid
Butyric acid	CH3-CH2-CH2-COOH	Found in butter
Caproic acid	CH3-(CH2)4-COOH	Found in butter
Palmitic acid	CH3-(CH2)14-COOH	Found in palm oil
Stearic acid	CH3-(CH2)16-COOH	Found in beef fat
Oleic acid	CH3-(CH2)7CH=CH(CH2)7COOH	Found in olive oil

Types of Fatty acids:

Saturated fatty acids, monounsaturated fatty acids, polyunsaturated fatty acids, and trans fatty acids are the four main classes of fatty acids.

Saturated fatty acids

The simplest fatty acids are unbranched, linear chains of CH2 groups linked by carbon-carbon single bonds with one terminal carboxylic acid group. When a molecule is said to be saturated, all feasible hydrogen bonds are made between every carbon atom in the molecule. Many saturated fatty acids have a trivial or popular name as well as a chemically detailed systematic term. Using the carbon atom numbers, starting with the acidic carbon, the systematic names are derived. The table includes the names and typical biological origins of the most prevalent saturated fatty acids. Fatty acids typically have chains between 12 and 24 carbons in length, however numerous shorter-chain fatty acids have significant metabolic roles as well. Butyric acid (C4) and caproic acid (C6) are two examples of milk lipids. Particular regions of the world rely heavily on palm kernel oil for their fat needs, and these regions benefit from the oil’s high concentration of fatty acids with 8 and 10 carbons (C8 and C10).

Unsaturated Fatty Acids

Unsaturated fatty acids have one or more carbon-carbon double bonds. The term unsaturated means that fewer than the maximum possible number of hydrogen atoms are linked to each carbon in the molecule. The generic name indicates the number of double bonds present; molecules with one double bond are called monounsaturated, whereas those with two or more double bonds are called polyunsaturated. The monounsaturated fatty acid oleic acid serves as an example. Common representative monounsaturated fatty acids coupled with their names and usual sources are included in the table. Palmitoleic acid’s cis-9 prefix indicates that the double bond between carbons 9 and 10 in the fatty acid’s structural formula. The two CH2 groups next to the double-bonded carbons can adopt either a cis or trans configuration. All biological unsaturated fatty acids have the cis configuration, wherein the two neighbouring carbons are on the same side of the double-bonded carbons. In the trans configuration, the two neighbouring carbons reside on opposite sides of the double-bonded carbons.

Polyunsaturated fatty acids :

Generally speaking, polyunsaturated fatty acids (those with more than one carbon-carbon double bond) are not abundant. The biosynthetic mechanism that introduces the double bonds into the hydrocarbon chain results in a regular spacing motif in which the multiple double bonds are separated by a CH2 group (CH2CH=CHCH=CHCH2). Linoleic and arachidonic acid, the two most frequent polyunsaturated fatty acids, are listed in the table, along with several others. Eicosanoids (from the Greek eikosi, “twenty”) are a group of chemicals that comprise prostaglandins, thromboxanes, and leukotrienes, and for which arachidonic acid (C20) is of special interest as a precursor. As discussed in the preceding section, intracellular and extracellular messengers, these chemicals, synthesised by cells under particular conditions, exhibit potent physiological effects. Animals must get the essential fatty acids linoleic acid (omega-6) and alpha-linolenic acid (omega-3 fatty acid) from plant sources because they cannot synthesis these two fatty acids themselves. These precursors are so crucial that they have their own name: essential fatty acids.

Trans polyunsaturated fatty acids:

Although mammals do not produce trans polyunsaturated fatty acids biosynthetically, these acids are made by microorganisms in the digestive tracts of ruminant animals like cows and goats, and they are also manufactured through partial hydrogenation of fats and oils during the production of margarine (the so-called trans fats). Adverse metabolic effects from consuming trans fats have been shown.

“Sources and uses of Lipids”

Origins (sources) of Lipids:

Animals:

• The majority of marine creatures, like whales and salmon, are excellent origins of lipids.
• An oil known as “cod liver oil” is extracted from salmon and whale.
• Animal milk also contains a significant amount of fat.
• Butter and ghee can be made from animal fat.

Plants:

The majority of plants are abundant origins of lipids, such as the oil-rich seeds of sunflower, corn, cotton, olive, coconut, and ground nut.

Application (uses) of Lipids:

• A fatty layer is present under mammalian skin that protects the inner organs from shocks because fat acts as an insulator
• A fatty layer is present around our heart and kidneys to protect them from injury.
• Some important vitamins, such as vitamin-A, vitamin-D, and vitamin-E, are essential for our body and can be obtained from lipids.
• Fats are the primary source of energy; they offer twice as much energy as carbohydrates. As a result, the body stores energy as fat and oil for later use. In the future, when a body experiences an energy crisis, these fats and oils will give the body enough energy to survive.
• The majority of commonly used items, including soap, detergents, polishes, paints, and cosmetics, are made from fats and oils. The oil can be turned into ghee by the hydrogenation process in the presence of a catalyst.
• Cholesterol, a lipid, is crucial for the production of hormones, bile acid, and vitamin D.

Note:

Animals alone are the source of cholesterol, including milk, meat, cheese, and eggs. Cholesterol does not originate in plants. Additionally, it has been noted that hens’ food contains flax seeds. These flax seeds reduce the cholesterol content of the eggs that these hens laid.

---

Related Biochemistry Posts

Biochemistry

Carbohydrates

Proteins