Final answer:
A steroid molecule includes a four-ring core structure with three cyclohexane rings and one cyclopentane ring, forming the backbone for biologically significant molecules like cholesterol and certain hormones.
Step-by-step explanation:
The molecule known as a steroid is characterized by a four-ring core structure. Specifically, there are three cycloalkanes that can be identified within this molecule. These are:
- Cyclopentane - A cycloalkane with five carbon atoms, forming a ring. It is the basis of the fifth D ring in the steroid structure.
- Cyclohexane - A six-carbon cyclic alkane, which constitutes the A, B, and C rings in the steroid skeleton.
- Another cyclohexane - As the structures may contain several six-membered rings.
These structures make up the steroid skeleton and are the fundamental components of various biologically significant molecules such as cholesterol, cortisol, and other hormones.