Final answer:
There are three types of hormones: lipid-derived, amino acid-derived, and peptide. Lipid-derived hormones can diffuse across cell membranes, while amino acid-derived and peptide hormones cannot.
Step-by-step explanation:
There are three types of hormones classified based on molecular structure and properties. Lipid-derived hormones, such as estrogen and testosterone, are lipid-soluble and can diffuse across cell membranes because they are non-polar. Amino acid-derived hormones, like epinephrine and norepinephrine, are relatively small molecules derived from the amino acids tyrosine and tryptophan. Peptide hormones, such as oxytocin and growth hormone, consist of polypeptide chains of amino acids. Unlike lipid-derived hormones, amino acid-derived and peptide hormones are water-soluble and insoluble in lipids, so they cannot pass through the plasma membrane of cells; their receptors are found on the surface of the target cells.