Ceramides are actually a family of lipids called waxy lipoproteins. A lipid is made of a single lipid molecule, which is composed mainly of a fatty acid and sphingolipids (cholesterol). Ceramic ceramides are very similar in structure to cholesterol and have similar lipophilicity (the ability to bind with lipids) but they have different biological functions. Ceramic ceramides can be classified as either endocytic or nonendocytic. Endocytic ceramides can easily penetrate into the cell and interact with receptor proteins.
Ceramides consist of a large number of lipids arranged in parallel strands. They can also be grouped into several sub-subsets. Some of these include: (1) triacylglycerols (TGs), (2} ceramides in liposomes, (3) ceramides in lipid vesicles (LCs), and (4) ceramides in lipid droplets. Ceramic ceramides can bind to lipids at the surface and interior of cell membranes. Ceramic ceramides can also bind to receptor proteins in the cell. In addition, they can also cause a change in the size of lipoprotein particles by changing their structure.
Ceramides can also be produced from triglycerides and cholesterol. Although ceramides cannot enter the body, they can be metabolized by the liver, which breaks down triglycerides to a degree. Ceramic ceramides are not produced in the body. Therefore, they are very low in concentration in the blood.