The Nobel Prize in Chemistry 2012 is awarded to Brian K. Kobilka and Robert J Lefkowitz for there study in G-protein–coupled receptors

G-protein–coupled receptors (GPCRs) form a remarkable modular system that allows 
transmission of a wide variety of signals over the cell membrane, between cells and over long 
distances in the body. Today, we understand the molecular mechanism of how these receptors 
work in intricate detail, in large part because of the studies by Kobilka and Lefkowitz.
Background
Every human cell is surrounded by a plasma membrane, a phospholipid bilayer. The 
membrane makes it possible for the cell to maintain a specific mix of biochemically active 
species, while preventing unwanted entry of other substances from the outside 
environment. For proper function, the biochemical machinery inside a cell needs to be able 
to receive instructions from the outside. 
Changes in hormone levels on the outside of the cell elicit adaptive changes in enzyme 
activity on the inside. Odour molecules affect cells in the olfactory epithelium and 
substances in the food influence chemical activities in tastebud cells, which in turn elicit 
electrical signals that transfer information to the brain. 
Indeed, human cells are constantly communicating with each other and the surrounding 
environment, which requires a molecular framework and a mechanism for transmission of 
information across the plasma membrane. Moreover, in the body, signal transmission may 
take place over long distances. To be able to respond promptly, the brain needs rapid 
information from our senses, for vision, smell, taste and more. Again, this requires a 
molecular mechanism for transmission of information over the plasma membrane. 

The molecular framework consists of G-protein–coupled receptors (GPCRs). Those are 
proteins located in the plasma membrane. The name GPCR refers to a common mode of 
receptor signalling via GTP-binding proteins on the inside of the cell. Because their 
polypeptide chain passes seven times through the plasma membrane, the GPCRs are also 
called seven-transmembrane (7TM) receptors. They mediate a wide range of physiological 
signals from the outside of the cell. The signal can be a change in concentration of peptides, 
hormones, lipids, neurotransmitters, ions, odourants, tastants, etc., or an influx of photons 
to the eye. GPCRs convey these signals to the inside of the cell and elicit a series of 
reactions involving other proteins, nucleotides and metal ions, which eventually deliver a 
message and an appropriate cellular and physiological response.
Many physiological processes in mammals depend on 7TM receptors, which are also the 
targets for a large portion of all pharmaceuticals drugs. About a thousand human genes 
code for 7TM receptors (1,2), and they are involved in sensing a wide range of extracellular 
stimuli. Examples include the adrenergic receptors, dopamine receptors, histamine 
receptors, the light receptor rhodopsin, and the many odor and taste receptors. 

Reference to   http://www.nobelprize.org/nobel_prizes/chemistry/laureates/2012/advanced-chemistryprize2012.pdf