Final answer:
Steroids are lipid-soluble molecules that travel in the bloodstream bound to transport proteins, enabling them to reach and diffuse into target cells where they regulate gene expression.
Step-by-step explanation:
Steroids, being lipid-soluble, are transported through the bloodstream by binding to transport proteins. These transport proteins keep the steroids soluble in the aqueous environment of the bloodstream, facilitating their transport to various target cells. Upon reaching a target cell, steroids can then diffuse across the cell's plasma membrane due to their lipid-soluble nature and interact with intracellular receptors present either in the cytoplasm or nucleus. This interaction leads to the regulation of gene expression, which in turn dictates cellular function and physiological responses.