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Unformatted text preview: Receptors & Signaling How do sex steroids interact w/ their receptors to give male or female characteristics? How does epinephrine signal “Fght-or-¡ight” using G proteins? How can insulin activating its tyrosine kinase receptor still result in diabetes? How do hormones signal? Hormone binds to complementary site on receptor 1) Peptide hormones bind to receptors on plasma membrane 2) Lipophilic hormones pass thru p. M. and bind to receptor in cytoplasm-> Receptor’s conformation and activity change-> Intracellular signaling path’s activity changes = Target cell response (depending on which receptors have bound the ligand) What hormones are lipophilic? Testosterone (ex. of androgen, produced in males’ testes) --> converted by aromatase (mostly found in ovaries) = estradiol (ex. of estrogen, produced in females’ ovaries). Why does a hormone bind to its own receptor?- High afFnity: chemical attraction btwn the two- Saturable: active sites can be Flled by available substrate- SpeciFc: complementary seqces btwn ligand and receptor - Reversible: hormone binding to receptor is not permanent -> regulation of binding = regulation of hormone action- How do you demonstrate hormone binding is reversible? If you add more h ormone, will more hormone bind its receptor?-Yes: positive correlation btwn the two...-Until all available receptors are bound to hormone = saturation Can you remove hormone from its receptor? I.e. Is binding reversible?-At 1.0 M labelled steroid bound, non-labelled steroid concentration = 0 M-As non-labelled steroid conc ups, labelled steroids is kicked off by non-labelled steroids = reversible binding-If irreversible, concentration of labelled steroid bound should remain at 1.0 M Aromatase (ovary) T t t E t di (ovary) 3 Testosterone...
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- Fall '11
- tyrosine kinase receptor, receptor kinase activity