In what category do steroids fall under in biological molecules?

Steroids are classified under lipids due to their hydrophobic nature and structural characteristics. They are composed of a carbon skeleton consisting of four fused rings, which is a defining feature of this class of molecules. Unlike proteins, which are made up of amino acids, or carbohydrates, which are primarily composed of sugars, steroids do not have a repeating unit but rather maintain a unique ring structure.

Moreover, steroids are involved in various biological functions, including acting as hormones (such as testosterone and estrogen) and playing roles in cellular membranes (e.g., cholesterol). Their lipid classification underscores their solubility properties, as they are not soluble in water but soluble in nonpolar solvents, which is characteristic of lipids. Thus, understanding the structure and functions of steroids within the lipid category is essential in biology and biochemistry.