Question

Draw on an 8.5 x 11 inch piece of paper the 2 signalling pathways (hormones- receptors- key signalling steps) that will converge to a single effect on the SAME cell (for example, lipolysis (fat breakdown). The later parts of the signalling pathways can be left in general terms, ie. “protein” phosphorylation, and lipolysis as a general term in the end. You do not need to provide more details on lipolysis. When the adipocyte effect of lipolysis is achieved BY BOTH HORMONES, draw the feedback loop(s) to the hypothalamus for ONE of the hormones.

**detailed description with words as well please

Answer 1

Lipolysis:

Epinephrine and glucagon

Receptor - G protein - 7 transmembrane protein. On the intracellular side, this G protein is associated with Gs G protein.

Secondary messengers - The Gs G activates adenyl cyclase enzyme - this enzyme converts ATP ( adenosine triphosphate ) into cyclic AMP.

An increase in cAMP stimulates protein kinase - this increases lipolysis.

Insulin -

Receptor - insulin receptor is a dimer of a heterodimer that consists of 2 alpha chain and 2 beta chain

Secondary messengers - stimulation of insulin receptor activation leads to the formation of insulin-like receptor substrate. These substrates activate phosphoinositol B kinase. this leads to the formation of protein kinase B

Protein kinase B stimulates phosphodiesterase 3B. this reduces the cAMP levels. the low levels of cAMP inhibits lipolysis

Insulin also enters the hypothalamus - it suppresses the lipolysis in the white adipose tissue.