Fatty Acids and Glycerides — Definition

Definition

Imagine lipids as a diverse family of biological molecules that don't mix well with water. Within this family, fatty acids and glycerides are two of the most important members, often working hand-in-hand.

Think of fatty acids as the 'bricks' and glycerol as the 'mortar' that together build larger lipid structures. A fatty acid is essentially a long chain of carbon atoms, typically 4 to 28 carbons long, with hydrogen atoms attached to them, and at one end, it has a special group called a carboxyl group (COOH).

This carboxyl group is what makes it an 'acid.' The length and the presence or absence of double bonds in the carbon chain determine its properties. If all the carbon-carbon bonds in the chain are single bonds, it's called a 'saturated' fatty acid, meaning it's 'saturated' with hydrogen atoms.

These tend to be solid at room temperature, like butter. If there are one or more double bonds between carbon atoms, it's an 'unsaturated' fatty acid. These double bonds introduce 'kinks' in the chain, preventing them from packing tightly, which is why they are typically liquid at room temperature, like olive oil.

Some unsaturated fatty acids, called 'essential fatty acids,' cannot be made by our bodies and must come from our diet, like Omega-3 and Omega-6. Glycerides, on the other hand, are formed when fatty acids chemically bond with a small, three-carbon alcohol molecule called glycerol.

This bonding process is called esterification, and the resulting bond is an 'ester bond.' Depending on how many fatty acids attach to one glycerol molecule, we get monoglycerides (one fatty acid), diglycerides (two fatty acids), or triglycerides (three fatty acids).

Triglycerides are by far the most abundant type of fat in our bodies and in the food we eat. They serve as the primary form of energy storage, packed away in fat cells (adipocytes) to be used when needed.

They also provide insulation against cold and protect our organs. So, in essence, fatty acids are the fundamental building blocks, and glycerides, especially triglycerides, are the major storage and functional forms of these building blocks in our biological systems.