Acylglycerides or fats are lipids formed by the esterification of one, two or three molecules of fatty acids with one molecule of glycerin (propanetriol). They are also called glycerides, glycerolipids, or acylglycerols.
There are three types, according to the amount of fatty acids that make up the acylglyceride molecule:
- Monoacylglycerides: contain a fatty acid molecule.
- Diacylglycerides: with two molecules of fatty acids.
- Triacylglycerides: with three molecules of fatty acids.
Fats, at room temperature, can be:
In cold-blooded animals and vegetables there are oils, and in warm-blooded animals there is tallow or lard.
Acylglycerides are not soluble in water because the polar hydroxyl groups (-OH) of glycerol are linked by an ester bond to the carboxyl groups (-COOH) of fatty acids. Triacylglycerides are considered neutral fats because they are nonpolar and insoluble in water. Monoacylglycerides and diacylglycerides have a weak polarity due to the hydroxyl radicals they release in glycerin. Acylglycerides when they react with bases, produce soap by saponification.
The detergent action of soaps is due to their tendency to form micelles. On the surface, in contact with water, the ionic ends of the salt remain, the carboxyl groups ionized, while the hydrophobic apolar chains are oriented towards the center, trapping insoluble particles, such as traces of dirt or drops of fat.
The most general function is to serve as an energy reserve for cells to which they supply fatty acids for fuel, which provide more energy than carbohydrates and proteins. They are also waterproof and good thermal insulators in animals, in which adipose tissue accumulates. In some animals with very cold environments, this tissue acquires a great development and constitutes the adipose pad.
