Question

what is a main difference between the modes of action of peptide hormones and steroid hormones?
multiple choice
peptide hormones bind to intracellular receptors, whereas steroid hormones bind to receptors on the cell surface.
peptide hormones act as second messengers, whereas steroid hormones bind to receptors in the cytosol.
peptide hormones bind to receptors on the cell surface, whereas steroid hormones act as second messengers.
peptide hormones bind to receptors on the cell surface, whereas steroid hormones bind to intracellular receptors
there are no differences; both act by binding to intracellular receptors.

Explanation:

Peptide hormones are water - soluble and cannot pass through the lipid - bilayer cell membrane. So, they bind to receptors on the cell surface. Steroid hormones are lipid - soluble and can pass through the cell membrane. They bind to intracellular receptors (either in the cytosol or nucleus).

Answer:

Peptide hormones bind to receptors on the cell surface, whereas steroid hormones bind to intracellular receptors.