Question

1. Describe the differences in transduction for steroid versus amino acid and peptide hormones. Describe at least one second messenger pathway in detail.

Answer 1

Steroid hormone are lipid soluble ,they can cross the lipid bilayer of plasma membrane .Receptors for Steroid hormones are intracellular ,they enter target cell and act directly on the intracellular receptor to produce their effect.Most polypeptide and amino-acid-derived hormones have there receptor present on the cell membrane of the cell .they bind to receptors located on the membranes of target cells.and Hormone-receptor complex forms which initiate the production of second messenger .Second messenger act on the target cell site and produce its effect.

Here is an example of secondary messenger pathway a peptide hormone(epinephrine).

• G-proteins are involved in this mechanism.It is a coupled receptor contains 3 subunits :alpha ,beta and gamma.

(i) Epinephrine Bind to the extracellular receptor present on the cell membrane and formation of hormone receptor complex takes place

(ii) G-protein activated and hydrolyses GTP to phosphorylate the G(alpha) subunit

(iii) Phosphorylated subunit bind with adenylate cyclase and activate it

(iv)Adenylate cycle convert ATP into cAMP

(v) cAMP activates Protein kinase -A

(vi)Activated Protein Kinase -Activates phosphorylase

(vii) Phosphorylase dephosphorylate the glycogen to form glucose and release in to blood.