Final answer:
Estrogen and testosterone are steroids used as hormones, while cholesterol is a steroid used as a component of membranes.
Step-by-step explanation:
The steroid used as a hormone is estrogen and testosterone. Estrogen is a hormone produced in the ovaries, while testosterone is a hormone produced in the testes. These hormones play important roles in the development of secondary sexual characteristics and the regulation of the reproductive system.
The steroid used as a component of membranes is cholesterol. Cholesterol is a lipid that is a major component of cell membranes. It provides rigidity to the membrane and is involved in various cellular processes, including cell signaling and transport of molecules across the membrane.