Final answer:
Cholesterol is the compound that is involved in hormone production, ensures membrane flexibility, and serves as a precursor to bile salts.
Step-by-step explanation:
The type of compound that functions in hormone production, contributes to membrane flexibility, and is the starting molecule for bile salts is cholesterol. Cholesterol is a steroidal compound synthesized by the liver and found in most animal-based foods. It is an essential component of cell membranes, contributing to their fluidity, and serves as a precursor to steroid hormones such as testosterone and estradiol. Furthermore, cholesterol is crucial in the production of bile acids, which aid in the digestion and absorption of dietary fats.