Final answer:
Steroid hormones synthesized in endocrine cells bind to transport proteins in the bloodstream, diffuse through the plasma membrane of target cells, and interact with receptors in the cytoplasm or nucleus to influence gene expression and regulate cell functions.
Step-by-step explanation:
Steroid hormones, which are made of lipids, can be found at different sites within a cell during the process of their production and secretion into the bloodstream. Initially, these hormones are synthesized in the endocrine cells where they diffuse across the membrane thanks to their lipid-soluble nature. Once outside these cells, they bind to transport proteins to remain soluble in the bloodstream.
At their target cells, steroid hormones are released from the transport proteins and diffuse across the plasma membrane due to their fat-soluble characteristics. Within the target cell, these hormones can bind to intracellular receptors located either in the cytoplasm or directly within the nucleus.
The hormone-receptor complex then influences gene expression by regulating specific genes, essentially acting as a transcription factor. This process modulates the synthesis of mRNA and the subsequent production of proteins, thereby regulating cell functions and activities.