The simple lipids are those whose composition involved oxygen, carbon and hydrogen. Its structure is made up of an alcohol and one or more fatty acids.
Lipids are ingested through foods such as dairy products, oils, fish, and nuts, among others. Once inside the body, lipids fulfill very important functions, such as protecting cells through the biological membrane, which covers these cells with a protective layer, which separates them from their environment.
Saturated fat molecule, a simple lipid
There is a general classification of lipids, according to which they can be unsaponifiable or saponifiable. Unsaponifiable lipids are those that do not contain fatty acids within their structure.
On the other hand, saponifiable lipids are those that do have fatty acids within their composition. Simple lipids fall into this category along with complex lipids, which are characterized by also having oxygen, carbon and hydrogen molecules, but also have sulfur, nitrogen and other elements.
Simple lipids are a large energy reserve in the body and are characterized by being not soluble in water.
Classification of simple lipids
Simple lipids are classified into two large groups: acylglycerides or fats, and cerides.
- Acylglycerides or fats
Example of acylglyceride, a triglyceride. Source: Wolfgang Schaefer
Acylglycerides are esters made up of glycerol, a compound that has been esterified by one, two or three fatty acids.
Esterification is the process through which an ester is synthesized. An ester is an element that arises from a chemical reaction between an alcohol and a carboxylic acid.
The reason that glycerol can react with one, two or three fatty acids is that each glycerol molecule has three hydroxyl groups.
Depending on the characteristics of the fatty acids that react with glycerol, acylglycerides are divided into two groups:
- Saturated fatty acids, which are those in which there are no carbon bonds between them (or double bonds between carbon and carbon), and have all the hydrogens that they can house within the structure.
Palmitic acid, a saturated fatty acid (Source: Wolfgang Schaefer / Public domain, via Wikimedia Commons)
These are generated by animals, and are also called fats. The saturated chain acylglycerides are characterized in that they are solid when they are at room temperature.
- Unsaturated fatty acids, which are those in which there are double bonds between carbons. These double bonds make the structure rigid and prevent the molecules from coming into contact with each other.
Structural formula of linoleic acid, a polyunsaturated fatty acid (Source: Jü / CC0, via Wikimedia Commons)
As a consequence of the separation of the molecules and the absence of interrelation in the unsaturated chains, this type of acid appears in a liquid state when it is at room temperature.
Unsaturated acids are generated only by plants, and are called oils.
There may be a third case, in which a glycerol links two of its carbons with two fatty acids through esterification, but the third carbon is attached to a phosphate group.
In this case, a phospholipid molecule emerges, one of whose most important functions is to form a structural part of the cell membrane.
Now, depending on the amount of fatty acids that make up an acylglyceride, three types can be described:
- When it is just a fatty acid attached to glycerol, it is called a monoglyceride or monoalziglyceride. These compounds have emulsifying and stabilizing properties.
- When they are two fatty acids linked to glycerol, it is a diacylglyceride or diacylglycerol. This acylglyceride can function as a transmitter of messages into cells.
- When there are three fatty acids (the maximum number of fatty acids that can exist in the structure) together with glycerol, it is called triacylglycerides or triglycerides. These fulfill energy storage functions; Most of the fatty acids in the body of animals are presented as triacylglycerides.
- Waxes or acidic acids
A honeycomb (Image by Pexels at www.pixabay.com)
These acids are characterized by having a more varied composition. Its basic structure is formed by the union of a fatty acid and a monoalcohol (that alcohol that has only one hydroxyl group), both composed of long chains; that is, both chains have a large number of carbons.
In addition to this structure, ceride acids have other elements, such as sterols, ketones, alcohols, among others. This combination of different compounds makes acidic acids highly complex structures.
The acidic acids, also called waxes, have waterproof characteristics, because their two ends are hydrophobic, that is, they reject water.
Waxes are solid when they are at room temperature and can change when pressure is applied.
The acidic acids are present in both animals and plants. In plants they fulfill a very important function, because they cover the stems, fruits and leaves, thus generating a protective layer that, in addition, makes it difficult for the plants to lose excessive water during the evaporation process.
In the case of animals, waxes can be found on the surface of the body, on the hair or feathers of the specimens.
Since the fundamental property of acidic acids is impermeability, the main functions of these acids have to do with processes in which they repel water and protect from external conditions.
Waxes are present in different areas. Some of its most outstanding uses and functions are the following:
- Ear wax prevents external elements from entering the ear canal, which could infect or cause damage.
- From the honeycombs, beeswax can be extracted, which has hydrating, antioxidant, humectant, anti-inflammatory and antibacterial properties, among others. Beeswax is often used for cosmetic purposes.
- There is a pictorial technique that consists of using waxes and other pigments in the generation of works of art. This technique is called encaustic painting. It uses a mixture of resin and beeswax called "medium", which is characterized by being shiny and hardening, so it does not need the use of protective glass.
- Waxes can also be used on textiles. In synthetic fiber fabrics, waxes reduce static electricity and create an even texture.
References
- "Complex lipids and simple lipids: structure and function" at the University of Seville. Retrieved on September 12, 2017 from the University of Seville: rodas5.us.es
- "Simple lipids" in Innatia. Retrieved on September 12, 2017 from Innatia: innatia.com
- "Lipids" at the National Institute of Educational Technologies and Teacher Training. Retrieved on September 12, 2017 from the National Institute of Educational Technologies and Teacher Training: educalab.es
- "Simple lipid" in Science Direct. Retrieved on September 12, 2017 from Science Direct: sciencedirect.com
- Busch, S. "What is the function of triglycerides?" in Muy Fitness. Recovered on September 12, 2017 from Muy Fitness: muyfitness.com
- "Acyl-Glycerides" at the National Institute of Educational Technologies and Teacher Training. Retrieved on September 12, 2017 from the National Institute of Educational Technologies and Teacher Training: educalab.es
- "The use of wax in industries" (September 12, 2012) in Marketizer. Retrieved on September 12, 2017 from QuimiNet: quiminet.com
- "Paraffins for textiles" (August 18, 2011) in Marketizer. Retrieved on September 12, 2017 from QuimiNet: quiminet.com.