G protein-coupled receptors (GPCRs) are the most prevalent gene family in the human genome. They are involved with everything from our sense of smell to immune system function to tumor growth. Unsurprisingly, GPCRs have been a hotbed for research and development. Of the 7,038 approved drugs analyzed for this blog post, I found that 29% of them target Class A (Rhodopsin-like) GPCRs, and 35% target any GPCR. In the spirit of Internet pop culture, I made a “quiz” to see if you can guess the top 10 receptors by their ligand’s chemical structure.