Fatty acids – monocarboxylic acids with the general formula R-COOH (R is a hydrocarbon chain and COOH is a carboxyl group located at the end of this chain). The concept of fatty acids is sometimes extended to all aliphatic non-cyclic carboxylic acids.
The hydrocarbon chain of natural fatty acids is usually straight (unbranched) and may contain several double bonds (Z configuration). For acids containing 10 or more carbon atoms, the term higher fatty acids is used. Natural fatty acids are made up of an even number of carbon atoms, and their number is usually 12-20. They differ from lower carboxylic acids mainly because they are insoluble in water and have a neutral pH due to the predominance of the hydrophobic over hydrophilic part. Fatty acids are often denoted in the notation n: m, where n is the number of carbon atoms in the molecule (including the atom contained in the carboxyl group), and m is the number of double bonds between them.
In nature, they occur in the form of esters with glycerin, i.e. fats, from which they are obtained by hydrolysis. Saturated fatty acids can also be obtained by catalytic hydrogenation of the corresponding unsaturated acids. Fatty acids are used for the production of soap, oil paints, medicines and cosmetics. In addition, they are used in the food industry (butter, oils, lard, margarine), and as fuels (stearin in candles) also in the form of fats (oil lamps).
Fatty acids play an important biological role, mainly as energy and reserve material. As a result of the β-oxidation process, Knoop are broken down into acetyl residues thioester-linked to coenzyme A. The resulting acetyl coenzyme A undergoes degradation with K oxid’s oxidation to CO2 and evolution of hydrogen atoms, which are then oxidized to water in the respiratory chain. Fatty acids are an important energy reserve, stored as triglycerides in adipose tissue. As a result of fatty acid oxidation, energy is needed for life processes.
They can be synthesized in the process of liponeogenesis.
Depending on the presence and number of unsaturated bonds, fatty acids are divided into saturated and unsaturated (monounsaturated and polyunsaturated).
Saturated fatty acids are fatty acids that do not contain double bonds between carbon atoms in the molecule. Under normal conditions, they are usually white solids. Acids containing more than 10 carbon atoms in the chain are insoluble in water and are not volatile.
Unsaturated fatty acids are fatty acids containing double bonds. They are usually colorless liquids. In most of them, all double bonds are in the cis position, and each double bond is followed by 3n (where n = 1, 2, 3 …) carbon atoms. In the case of unsaturated fatty acids, the notation n: m is not enough. The position of the double bonds should also be indicated, which can be done in two ways:
• using the notation delta-k, l, m …, i.e. Δk, l, m …, where k, l, m … denote the position of the double bond counting from the carboxyl group (e.g. the notation Δ9,12 means, that the double bonds are at 9 and 12 carbon) or
• using the omega-i notation, that is, ω-i or n-i, where i denotes the location of the last double bond from the end of the carbon chain (e.g. omega-3 means that the last double bond is at the third carbon from the end). Omega-3 and omega-6 fatty acids are described in more detail in separate articles.
Among unsaturated fatty acids there is a group of polyunsaturated fatty acids which, as the name implies, contain more than one double bond. They are an essential element of the human diet (they are a group of so-called vitamin F, otherwise exogenous or essential fatty acids), because we need them to form important compounds (e.g. prostaglandins), and are not synthesized by human organisms (only plants and some animals (e.g. fish oil).
Cis isomers of fatty acids occur in nature, while trans isomers are formed as a result of industrial processing of fats. It was found that fats containing the form of trans fatty acids are harmful to health resulting in atherosclerosis and therefore their intake should be limited.
The more important unsaturated fatty acids are:
• monounsaturated (monoenic) acids, containing one double bond:
o 16C oleopalmitic acid (containing 16 carbon atoms in the molecule)
o 18C oleic acid
for erucic acid 22C
for 24C nervous acid
• di-unsaturated (diene) acids, containing 2 double bonds:
for 18C linoleic acid
• tri-unsaturated (triene) acids, containing 3 double bonds:
o α-linolenic acid 18C
o 18C-linolenic acid
• tetra unsaturated (tetraenoic) acids, containing 4 double bonds:
for 20C arachidonic acid