Part 2. Biosynthesis and Metabolism

All eukaryotic organisms and even a few prokaryotes have the ability to synthesise triacylglycerols, and the process has been studied intensively in plants and animals especially. Many cell types and organs have the ability to synthesise triacylglycerols, but in animals the liver, intestines and adipose tissue are most active with most of the body stores in the last. Within all cells, even those of the brain, triacylglycerols are stored as cytoplasmic ‘lipid droplets’ (also termed ‘fat globules’, ‘oil bodies’, ‘lipid particles’, ‘adiposomes’, etc) enclosed by a monolayer of phospholipids and hydrophobic proteins, such as the perilipins in adipose tissue or oleosins in seeds. These lipid droplets are now treated as distinctive organelles, with their own characteristic metabolic pathways and associated enzymes – no longer boring blobs of fat. They are not unique to animals and plants as Mycobacteria and yeasts have similar lipid inclusions.