Steroid hormones have

• A. 3 rings
• B. 5 rings
• C. 4 hydrocarbon rings
• D. 2 rings

Answer: (C)

Steroid hormones share a four-ring hydrocarbon backbone, the steroid nucleus, which comes from cholesterol. This structure is made of three six-membered rings fused to one five-membered ring, giving a total of four rings. That four-ring framework is what defines steroids and sets them apart from molecules with fewer or more rings. Because of this hydrophobic scaffold, steroid hormones diffuse through cell membranes and bind to intracellular receptors that act as transcription factors to regulate gene expression. The other ring counts don’t match the classic steroid structure, which is why four rings is the correct description.