Explain mechanism of peptide homones action.

Explanation

1. Hormones are classified into three major groups as peptide hormones streroid hormones and amino acid derived hormones based on their chemical structure
2. Peptide hormones cannot cross the phospolipid cell membrane and bind to the receptors on the exterior cell surface.They are are transported to the golgi , which is the site of modification.it acts as a first messenger in the cell
3. Hormones on binding to their receptors do not enter the target cell but genrate the production of second messengers such as cyclic AMP (cAMP) ,which in turn regulates cellular metabolism .this is catalyzed by the enzyme adenylate cyclase.
4. The interacton between the hornmone at the surface and the effect brougth out by cAMP within the cells is known as signaling cascade .At each step there is a possibility of amplification
(i) One hormone molecule may bind to multiple receptor molecule before it is degraded
(ii) Each recepter may activate serval adenlate cyclases each of which make much cAMP
(iii) Thus there is more signal after each step . The actions of cAMP are terminated by phosphodiesterases . The effect of peptide hormones like insulin glucagon somatotropin are usually short lived becauses they work through second messenger system.