Final answer:
Steroids are a major class of lipids with a characteristic four-ring structure, including compounds like cholesterol and hormones such as cortisone and estrogen.
Step-by-step explanation:
Steroids are a major class of lipids. These compounds are characterized by a four-ring structure and are hydrophobic, making them insoluble in water. Notably, steroids do not resemble other lipid types such as fats or phospholipids in their structure but are nevertheless categorized with them due to their chemical properties.
An example of a steroid is cholesterol, which plays a critical role as a component of cell membranes. Moreover, many steroids function as hormones in the body, including cortisone and sex hormones such as estrogen. Sterols are a subclass of steroids that include compounds like cholesterol that have the -OH functional group.