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Describe the diversity of function found in proteins using examples. 

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brandih | eNotes Employee

Posted September 16, 2013 at 7:25 PM via web

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Describe the diversity of function found in proteins using examples. 

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ncchemist | eNotes Employee

Posted September 25, 2013 at 2:19 AM (Answer #1)

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Brandi I am going to assume that the (8+1+1) typed in your question is some type of error because I cannot figure out what it would mean in this context.

Proteins are essentially long polymeric chains built up of amino acids.  Most proteins are built from the same set of 20 of the most common amino acids, but the huge numbers of the various combinations of these amino acids means that there are almost endless possibilities for the number of possible proteins.  Each amino acid contains a unique chemical group called the side chain.  Some of these side chains are alkyl groups (hydrophobic), others are highly polar groups or salts.  It is the chemical and electrostatic nature of these side chains combined with the folding of a protein in 3 dimensional space that gives rise to the diversity of functionality found in the protein world.

Due to the above mentioned factors, proteins have the unique ability to bind to very specific molecules called substrates depending on the nature of the specific protein.  These substrates can be either small molecules or other proteins themselves.  The specificity of the binding is incredible.  Even a tiny change in the structure of the substrate can make it go from an excellent protein binder to a poor one.  This is because the site on the protein where the substrate binds (called the active site or binding site) has particular amino acid side chains located at very specific points that are designed by nature to specifically interact with a specific substrate and nothing else.

There are three major types of proteins that all have a different function.  The first type are called enzymes.  Enzymes are proteins that are designed to catalyze specific chemical reactions in a biological system.  There are literally countless enzymes in nature.  One example is an enzyme called alcohol dehydrogenase.  It is used by bacteria during fermentation to reduce a carbonyl group to an alcohol group, thus producing ethanol during the fermentation process to make beer or wine.

The second type are involved in cell signalling pathways.  Most cell membranes contain proteins embedded in them.  When the specific substrate binds to the membrane bound protein, it induces a conformational change (or a change in shape) of the protein that is relayed through the cell membrane to the inside of the cell.  This conformation change then signals a particular chemical pathway within the cell to elicit some kind of function.  A popular example of these type of proteins are called g-protein coupled receptors (GPCR's).

The third type are structural proteins.  These are probably the least interesting as they only serve to provide structural integrity to a biological system.  Collagen is an example that serves to provide structural support to skin, ligaments, and tendons.

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