Chemistry in Biology

The Nobel Prize in Chemistry for 2012 was awarded to two Americans who have worked to elucidate the structure and function G- Protein Coupled Receptors or GPCR's. 

 This article "Cells and Sensiblity" is written at a level that IB students should be able to handle after their studies of HL Membrane proteins and HL Protein structure as well as Option H Hormones. This article "G- Protein-Coupled-Receptors" provides the scientific background for the work and should support teachers in understanding the details.

This award recognises the work that explains how substances and even photons of light can prov

oke cellular changes that result in physiological reactions from celluar secretions to nerve impulses of retinal cells.  Earlier Nobel Prizes have been given for the discovery of the secondary messenger cAMP and the enzyme adenylyl cyclase which act inside the cells but how the signal of the external stimulus passed through the membrane had remained a mystery.

In the 1970's, Robert Lefkowitz began studying how a hormone could bind to cell membranes of adrenal gland cells causing the production of adrenalin or epinephrine and it was this work which allowed for further studies in the binding of substances to the receptors which was recognised for the Nobel Prize this year.

In the 1980's, Brian Kulpika sequenced the gene for the receptor.  For over twenty years, Kulpika searched for the structure of the receptor by x ray crystallography but the fact that the protein has large zones of nonpolar amino acids so that it resides within the phospholipid bilayer made the process very difficult.  It was in 2011, the structure of the receptor was deduced through a detailed image. The images revealed a protein with 7 alpha helices, supporting the transmembrane nature of the protein. More spetacular was that the protein was in the process of transferring the signal across the membrane, illustrating the function of the receptor.  This was the decisive step that earned Kulpika the Nobel Prize in 2012. 

Sequencing of the human genome aided the development of this work as whole families of GPCR's were found by comparing the simlarity of sequences in the helical structures.  An example of these similarities can be seen in the articles.

The articles link to the Noble Prize site provide an exciting opportunity for students to see that the material they are studying is relevant and current, that they are learning about things that have taken many people over many years to understand.  I suggest using this to stimulate and encourage students to ask questions about what they are studying.