Fatty acids are often confused with fats, especially by people who hail from non-science backgrounds. However, fatty acids are not fats. Fatty acids are formed by the hydrolysis (splitting with water) of triglycerides (ester) which occur in vegetable oils, animal fats etc. Fatty acids either remain free in the body or get attached to other molecules. These chemical compounds are of great importance to human beings. They, when metabolized, yield large amounts of energy, which is essential for the normal functioning of muscles, heart, and other organs. However, brain cannot depend on fatty acids for energy; it derives energy from glucose and ketone bodies. Fatty acids act as building blocks for cell membranes and also as energy storing compounds. Those fatty acids not used up as energy get converted into triglycerides and are stored in the adipose tissues of the body for future use. Fatty acids are classified into various types depending on their chemical structure and synthesis. Read further to know more details about the types of fatty acids.
Chemistry Of Fatty Acids
Before getting into the types of fatty acids, it is important to know their chemical structure, functions and physiology. Fatty acid is a carboxylic acid (organic acid with carboxyl group) with a long aliphatic carbon chain. This carbon chain may either be saturated (all single bonds) or unsaturated (one or more double bonds). Most naturally occurring fatty acids have even number of carbon atoms in their carbon chain.
Short-chain and medium-chain fatty acids are directly absorbed into the blood through intestine capillaries and are then transported just like other nutrients. Long-chain fatty are absorbed into the intestine villi and are then broken down into triglycerides. These triglycerides are then coated with cholesterol and protein to form a compound called chylomicron, which is then transported and stored.
Types According To Length
Short-chain Fatty Acids (SCFA): These have less than six carbon atoms in their aliphatic chain (acyclic or cyclic non-aromatic compounds). Acetic acid (2 carbon atoms) is an example of Short-Chain Fatty Acid.
Medium-chain Fatty Acids (MCFA): They have six to twelve carbon atoms in their aliphatic chain.
Long-chain Fatty acids (LCFA): They have twelve to twenty two carbon atoms in their aliphatic chain. Palmatic Acid (16 carbon atoms) is an example of Long-chain fatty Acid.
Very Long Chain Fatty Acids (VLCFA): They have more than twenty two carbon atoms in their aliphatic chain. Examples for Very Long Chain Fatty acids are lignoceric acid (24 carbon atoms) and hexacosanoic acid (26 carbon atoms)
Types According To Presence Of Double Bonds
Saturated Fatty Acids: Saturated fatty acids are long chain fatty acids which lack double bonds between carbon atoms in their structure. Their bonds are highly saturated with hydrogen atoms. Carpylic acid is an example of saturated fatty acid.
Unsaturated Fatty Acids: These are fatty acids with one or more double bonds between carbon atoms. They are called unsaturated fatty acids because, their double bonds are unsaturated. They can be saturated by adding hydrogen atoms and thus, converting the double bonds into single bonds. The carbon atoms on both sides of the double bond can occur in two different configurations namely ‘cis’ and ‘trans’. Myristoleic acid is an example of unsaturated fatty acids.
Types According To Dietary Requirement
Essential Fatty Acids: Human beings require fatty acids for their normal body functioning. Of course, human body synthesizes fatty acids but, not all of them. We need to supplement our body with fatty acids which are not synthesized in our body. Such fatty acids, which can be obtained from food, are called essential fatty acids. Linoleic acid is an essential fatty acid.
Non-Essential Fatty Acids: Non-essential fatty acids are those which can be synthesized in our body and hence, we can meet the requirement even if they are not supplemented though food. The name non-essential does not mean that they are not essential for normal body functioning. Many of these non-essential fatty acids are involved in important body functions. They are called non-essential because we need not intake them as a part of our diet as they are synthesized by our bodies internally. Oleic acid is a non-essential fatty acid.
Free Fatty Acids
In animals, lipid (fat) metabolism also produces free fatty acids. These fatty acids are later esterified and utilized for various purposes. So, free fatty acids are not a type of fatty acid, but only a stage in their metabolism. Such fatty acids are insoluble in water and hence, they are bound to plasma protein albumin for transportation. The levels of "free fatty acids" in the blood are limited by the availability of albumin binding sites. Free fatty acids are very important chemical compounds. They have potent antiviral, antimicrobial and antifungal properties, and hence, protect skin and mucosa of the lung from any infections. They are capable of inhibiting many enzymes systems in a non-specific manner. They have biocidal (antibiotic) properties also, but it is not sure whether these properties are non-specific or not.
Hope now you have an idea about what are fatty acids and why are they so important. The classification mentioned above depend on various criteria and so, some of them may belong to more than one type.