Welcome to an Amoeba Sisters short on lipids. We’ve mentioned a few functions of lipids: they can be sources of long-term energy, make up cell membranes, provide insulation, function as some hormones. But much of this depends on what type of lipid we’re talking about as this is a diverse group. One thing lipids share: they are hydrophobic or at least contain a significant hydrophobic component. As a fat, lipids have two types of building blocks: a glycerol and fatty acids. A triglyceride is a fat. Whether fats are saturated or unsaturated depends on the fatty acids: unsaturated fatty acids generally have 1 or more double bonds making them less saturated with hydrogens. Then there are phospholipids – these lipids have a polar hydrophilic head with a nonpolar hydrophobic tail. They make up our cell membranes. Steroids are also lipids – always wow to me- and an example includes cholesterol which has a role in cell membranes. Some hormones are also steroids.