Lipids are a group of biological compounds that are classified together by their structure, generally apolar (carbon, hydrogen and oxygen), which makes them poorly soluble in water. They are made up mainly of fatty acids and glycerin or other alcohols. They are usually classified into glycerides (oils and fats), phospholipids, sphingolipids, glycolipids, cerides (waxes), steroids and terpenes. Fats and oils are the most abundant, they are the main constituents of the cells that store them in animals and plants, and they make up one of the important food reserves of the body. The difference between fats and oils is very clear;oil is a liquid at room temperature, while fat is solid. These can be extracted from animals and vegetables, thus obtaining substances such as corn oil, coconut oil, palm oil, tallow, fat from bacon and butter.
From a chemical point of view, they are fatty acid esters, formed by esterification reactions between them and an alcohol (glycerol). Three fatty acids are attached to each glycerol molecule, from which the word triglycerides derives. Fatty acids are made up of long hydrocarbon chains, saturated (with single bonds) or unsaturated (with double bonds). Animal fats tend to be saturated, while most oils are unsaturated (except palm oil, coconut oil, and cocoa butter).
Fats are more concentrated in dietary energy (calories) than carbohydrates and proteins. For this reason, when small amounts of fat or oil are added to food, its caloric value increases significantly. Fats, in addition to storing energy for times of need, protect body organs (kidneys, adrenals) from damage, insulate the body against cold and help shape and develop the body to give it shape and beauty. Unfortunately, the excess calories or energy from overeating, even from low-fat foods, is also stored as fat and leads to obesity.
The other lipids also play fundamental roles as components of the membrane structure (phospholipids); waxes form protective surfaces on the leaves and fruits of higher plants, on the cuticle of insects and on the epidermal formations of birds and mammals. Steroids give rise to a huge variety of active biomolecules such as hormones (testosterone, estrogens), sterols, toxins and poisons, they also include vitamin D; and finally, terpenes, essential oils that give many fruits, rubber and some vitamins their characteristic color.
