Distinguish between the mode of action of steroid hormones and protein hormones.
Steroids enter the cell directly because they are lipid soluble, or non polar. The receptor is internal, and is located within the cytoplasm. The steroid binds to the receptor. The hormone receptor complex enters the nucleus and triggers the transcription of a gene. This causes production of a certain protein
Steroid --> Receptor (in cytoplasm) ---> Hormone Receptor Complex ---> nucleus --> transcription of a gene
Protein hormones bind to receptors in the membrane. They can't enter the cell because they are polar, water soluble, and very large. This initiates a series of chemical reactions that produce a second messenger inside of the cell which alters some cell function. This is called signal transduction. This can include altering the transcription or expression of the gene or, more often, the activation of an enzyme.
Protein hormone --> Membrane receptor --> chemical reactions in cytoplasm --> second messenger --> change in cell function or transcription