Meaning of Lipid
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, these are the main constituents of the storage cells of these in animals and plants, and they make up one of the important food reserves of the body .
This term has its origin under the Greek λιπος, whose meaning refers to lipos, that is, fat , from there, other terms such as dyslipidemia and lipoma derive. But it is also composed by the Latin ido, which refers to an appearance in different chemical compounds such as nucleotide, acid and hydroxide.
Now, entering the subject well, lipids are nothing more than various molecules found in the body, some are formed by a type of aliphatic chain, which can be both saturated and unsaturated, but there are also others that have apparently aromatic rings .
Within the structure of lipids , there are very flexible molecules, some semi-flexible and a minority rigid. What do you mean by that? that these molecules are very varied and have different compositions (some with hydrogen bonds and others with free-type carbons). Everything related to this term will be fully explained throughout this post.
Classification of lipids
This type of molecules make up a heterogeneous group divided into two aspects, so that they can attend to the composition of lipids, that is, those that are made up of fatty acids that are known as saponifiable and unsaponifiable.
Saponifiable lipids
These are those that are similar to waxes and their main characteristic is to hydrolyze, these are classified into simple and complex.
- Simple : these types of molecules are composed of oxygen, hydrogen and carbons, this converts them into acylglycerides, but also, they are glycerol esters with fatty acids. These molecules are called fats only when they are solid, otherwise they are called oils and their function is to store all kinds of energy.
- Complex : these are molecules composed of 3 chemical bases (that is, oxygen, hydrogen and carbon) and other complex nutrients, these are sulfur, nitrogen, phosphorus and carbohydrates. These lipids are considered membrane because they make up the cell membranes of the human body. Their function is purely structural because they make up the biological membrane, that is, the natural membrane of the living being.
Unsaponifiable lipids
They are those that, unlike the previous aspect, do not have the ability to hydrolyze when faced with hydroxides, this includes terpenes, steroids and prostaglandins.
Simple lipids
As mentioned before, these are molecules that are made up of three base chemicals and have a special structure based on fatty acids and alcohol. Its classification is based on fatty acids, acylglycerides and cerides.
Fatty acids
From the 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 the body's organs (kidneys, adrenals) from damage, insulate the body against cold and help shape and develop the body to give it shape and beauty. Unfortunately, excess calories or energy from overeating , even from low-fat foods, is also stored as fat and leads to obesity.
- Saturated fatty acids : they lack double bonds with respect to carbon atoms, an example of lipids of this type are lauric, margaric, myristic, arachidic, palmitic, stearic and lignoceric acid. Its function is to provide energy to the human body .
- Unsaturated fatty acids : they are characterized by having double bonds, they achieve that their fusion or combination is less compared to the others. These fats or lipids are the well-known oils.
These types of lipid foods lower cholesterol levels in the blood. In this aspect, humans differ greatly from animals, since the latter cannot synthesize these acids, this makes the function of lipids in them is clearly physiological (to care for hair and skin) and they must be ingested in their diet daily. - Essential fatty acids : these are fatty acids that the body does not synthesize, therefore, it is important to include them in daily diets , in this way, when ingested, the body takes the ability to synthesize the rest of the lipids it needs to store energy and perform various important functions in the body.
Acylglycerides
Acylglycerides or fats are lipids formed by the esterification of one, two or three molecules of fatty acids with a molecule of glycerin (propanetriol). They are also called glycerides, glycerolipids, or acylglycerols. 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 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 from very cold environments, this tissue acquires a great development and constitutes the adipose pad.
There are three types, according to the amount of fatty acids that make up the acylglyceride molecule and they will be explained below:
- Monoacylglyceride : the composition of monoacylglyceride lipids is based on glycerol, which binds with fatty acid chains. I can do this through an ester bond. Each of them can be very different , some can be liquid solids, waxy or hard solids, each one insoluble in liquids such as water or soluble in organic solvents, therefore, it tends to refer to lipid metabolism, that is, to the synthesis of lipids. These have the ability to lower the tension between high temperature lipids and water.
- Diacylglyceride : it is also made up of glycerol, but this is esterified with two other fatty acids . Its function is to catalyze enzymes, because they perform a type of cellular signaling.
- Triglycerides : these are esters derived from three fatty acids and glycerol, which is why their name begins with tri. They are important because they are the ones that provide body fat in living beings, that fat is vegetable.
Cerids
Cerides, also known as waxes, arise from the union of a long-chain fatty acid (from 14 to 36 carbon atoms) with a monoalcohol, also long-chain (from 16 to 30 carbon atoms), through a ester bond. The result is a completely apolar molecule, very hydrophobic, since no charge appears and its structure is of considerable size.
This characteristic allows the typical function of waxes to be waterproofing . The layer of young leaves, fruits, flowers or petals and the integuments of many animals, hair or feathers, are covered with a waxy layer to prevent the loss or entry (in small animals) of water.
Phosphoacylglycerides are composed of glycerol , two of whose -OH (hydroxyl) groups are attached to two fatty acids via individual ester bonds. The third is related to the phosphate group, also via an ester bond, which in this case is commonly referred to as the "phosphodiester bond".
Complex lipids
As mentioned before, they have a special composition and very different from the simple ones, but they also have their own classification and it will be explained below.
Phospholipids
They have a rather peculiar characterization because they have phosphate , which gives them a fairly marked polarity. These also have their classification and are divided into two aspects, which differ because one has glycerol and the other sphingosine.
- Lipoproteins : they are a set of macromolecular elements, which are made up of both lipids and proteins , which are responsible for the transfer of large amounts of fat throughout the body.
Regarding their structure, they are wrapped in a polar cortex, which is composed of phospholipids, lipoproteins and free cholesterol, within said cortex the nucleus of this macromolecule is located, consisting of triglycerides and esterified cholesterol. Lipoproteins are characterized by being water soluble and having a spherical shape. Some examples of lipoproteins are antigens, enzymes, and certain toxins.
The main function of lipoproteins is the transport of fat through the bloodstream to the different tissues of the body, as well as in the opposite direction, that is, from the tissues to the liver.
- Phosphoglycerides : they are made up of an acid called phosphatidic, which in turn is made up of phosphoric acids and combines with hydrogen. This molecule is quite complex because it also has glycerol and other fatty acids, one unsaturated and the other saturated, also adding phosphate and its function is clearly structural in the cell membrane.
- Phosphoesphingolipids : the composition of lipids of this type at the molecular level is very similar to phosphoglycerides, but, unlike the previous ones, they do not have glycerol , instead they have sphingosine. They serve as antigens in the human body.
Glycolipid
It is a series of sphingolipids that are composed of a ceramide of aminoalcohol and fatty acids that, in turn, is linked to a species of carbohydrate, this means that it does not have a phosphate group. The lipid profile of this slope is classified into two groups, the first is cerebrosides and the second is gangliosides.
- Cerebrosides : it is a group of glycolipids that have ceramide linked to a monosaccharide, that is, to lactose or glucose, but it can also be linked to an oligosaccharide. These regulate every component of the membranes of the nervous system.
- Gangliosides : it is a group of glycolipids in which ceramide is linked to a rather complex oligosaccharide because it always has sialic acid within its composition. They work to regulate the properties of the membranes of the nervous system.
Unsaponifiable lipids
These types of molecules are classified into three aspects , which are distributed among isoprenoids, steroids and prostaglandins.
Isoprenoids
Isoprenoids, sometimes called terpenes, are a large and diverse class of naturally-occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures that differ from each other not only in functional groups, but also in their basic carbon skeletons. These lipids can be found in all classes of living things, and they are the largest group of natural products. About 60% of known natural products are terpenoids.
- Characteristics : isoprenoids are hydrocarbons resulting from the condensation of several 5-carbon isoprene units. The isoprene unit has the formula CH2 = C (CH3) CH = CH2. Terpenoids can be thought of as modified terpenes , in which methyl groups have been moved or removed, or oxygen atoms have been added. Like terpenes, terpenoids can be classified according to the number of isoprene units used.
- Functions : Terpenoids can also be classified according to the number of cyclic structures they contain. The Salkowski test can be used to identify the presence of terpenoids. Meroterpenes are any compound , including many natural products, that have a partial terpenoid structure.
Steroids
Steroids are hormones that occur naturally in the body and are born from organic compounds resulting from a molecule called cyclopentaneperhydrophenanthrene, also known as steran. This hormone is secreted by the glands of the body and, in this way, is distributed throughout the bloodstream. Steroids form hormones and vitamins creating four linked rings. Three of them with six particles and one with five, having a total of 17 carbon particles. In steroids this major organization is changed by the addition of several practical sets, such as carbonyls and hydroxyls (hydrophilic) or hydrocarbon crosses (hydrophobic).
- Characteristics : the steroid core is very rigorous and has a usually flat distribution. The components that come out of this nucleus have methyl sets (-CH3) in place 10 and 13, symbolizing carbons 18 and 19, also since a carbonyl or a hydroxyl at carbon 3, usually there is a hydrocarbon chain at the same time stuck at carbon 17, the existence of methyls, hydroxyls or carbonyls and the amplitude in the chain establish the various structures of the substance.
- Functions : steroids are defined by exercising various functions in the internal part of the human body . One of the main functions is to regulate the metabolism of the main macronutrients, which consists of fats, carbohydrates and proteins. In the same way, they serve to save the proportions of electrolytes and homeostasis that is responsible for balancing important movements since it must keep the same level of water in the cells of the body. In the same way, they keep the cardiovascular, nervous, musculoskeletal and renal systems in an optimal state.
Prostaglandins
It is a series of molecules that are derived from essential fatty acids, which are composed of 20 carbons with a type of omega 3 and omega 6. All this leads to the creation of a group of lipid substances that, in turn, they have a cyclopentane ring and make up the group of cellular mediators.
- Characteristics : its precursors are linoleic, arachidonic and linolenic acids.
- Functions : the function of prostaglandin lipids is to serve as a type of mediator for the nervous system and thus support immune processes and responses. They are also part of the cellular communications found within the organism of living beings such as animals and humans.
Importance of lipids
When talking about the importance of these molecules, reference is made to lipid digestion . Why? because there are some vitamins such as A, E, D and K that are fat soluble and can be digested, absorbed and transported together with the fats that are located in the body. In addition, the structure of lipids is of great importance in terms of fats because they keep the skin and hair healthy, keep the body temperature at a perfect level, reserve energy and allow the synthesis of other acids.
Dyslipidemia
This term is related to the imbalance of lipid levels in the blood . It is important to remember that lipids are essential for life because they produce energy and provide other benefits, in addition, these are distributed throughout the body through blood flow. When these lipids are altered because there is an excess of them in the blood, the body begins to suffer from dyslipidemia.
Causes
There are two fats that are recommended to monitor, these are cholesterol and triglycerides . A variation in the levels of these fats can cause serious damage both in the arteries and in the brain and heart. If the cholesterol level exceeds its normal values, it is because it is accumulating inside the arteries, causing them to harden, thus preventing oxygen from reaching the brain and heart, producing serious consequences.
Specialists consider that a high level of cholesterol , accompanied by other elements of vascular risk such as diabetes or smoking, can be the cause of possible arterial and cardiovascular damage, a result of this is that the patient suffers from heart attacks or strokes .
Lessons
There are two types of dyslipidemia that are classified as primary hyperlipidemia and secondary hyperlipidemia , either group represents a danger to the human body because it can trigger cardiovascular problems.
- Primary hyperlipidemia : it originates from the abuse in the consumption of saturated fats , causing arteriosclerotic lesions.
- Secondary hyperlipidemia : it is linked to the variations in lipid metabolism that occurs when the person suffers from diabetes, kidney disease, which is caused by excessive alcohol intake and the consumption of diuretic drugs.
Consequences
Unlike other diseases, dyslipidemia does not have any type of symptoms , which is why it is considered a totally asymptomatic pathology. When doctors detect the disease, it has advanced too far and can lead to strokes, coronary heart disease, and pancreatitis.
Treatment
The best way to combat dyslipidemia is to eat a healthy diet , do physical activities, take your medications previously prescribed by your treating doctor, etc. Specialists recommend the following to prevent and control dyslipidemia: Reduce the consumption of foods with a high content of fats and sugars; restrict the consumption of alcohol and tobacco; increase the consumption of fruits and vegetables, do physical activities at least 30 minutes a day , etc.