Peptides are chains of amino acids, typically two or more, while steroids have a four-ring structure derived from cholesterol. Peptides are water-soluble, involved in signaling, and play roles like hormone production (e.g., insulin). Steroids are fat-soluble, serve as hormones or vitamins, and include examples like testosterone and estrogen. The main differences lie in their structure, solubility, function, and source. | #emises