What is the main function of steroids in biological systems?

The main function of steroids in biological systems is to serve as hormones and signaling molecules. Steroids, which are a type of lipid characterized by a carbon skeleton with four fused rings, play a crucial role in regulating various physiological processes in the body. These hormones, such as testosterone, estrogen, and cortisol, act by binding to specific receptors in target cells, initiating a cascade of biological effects that influence metabolism, immune response, growth, and reproductive functions.

Their ability to pass through cell membranes due to their hydrophobic nature allows them to interact directly with the internal machinery of cells, unlike some other signaling molecules that cannot easily cross the membrane. This means that steroids can exert their effects at very low concentrations and have long-lasting actions, which is vital for maintaining homeostasis in biological systems.