MIRACLES OF OUR TIME

Protein Synthesis (According to George)

“My name is George, I am a protein, and I work in one of the waste disposal plants in my home cell.  Actually the last time that I was out of the plant was when I was brought here a long time ago to begin my career in waste disposal. I am now reaching the end and will retire shortly as soon as my replacement arrives.  It has been a good job and I have enjoyed working side by side with other workers who are exactly like me.  At least they were like me when I began, but parts of me have been wearing out.  Our job is to tear apart industrial waste so an acid bath can dissolve it more quickly.  This requires strength, which is what I have, in spite of my roly-poly shape. In watching my fellow workers over my career, I have come to the conclusion that we have the perfect shape for our job.  The bosses must think so also because whenever a replacement comes, he is just like us when we began.  No new improved versions among them.  So I figure the reason for that is you can’t beat perfection.

“Being quite an observant fellow, I have noticed that my fellow workers and I are made of twenty kinds of pieces that are joined like links on a chain.  I have counted 482 but since our shape, as I already mentioned, is roly-poly, some of the links are hidden inside and cannot be counted.   I vaguely remember a time when I was long and sleek, before my 500 or more pieces were folded into my present shape.  With the help of my memory, poor as it is, and questioning my bosses and recently-arrived workers, I have figured out how we were made. If you have a few minutes, I would like to tell you.”

The Cell Library (The Nucleus Containing the DNA)

“First I learned that my cell has a library that contains the instructions for making me, all the other proteins in my plant as well as the proteins everywhere else in my cell. (This cell is quite a place.)  I prefer to call the instructions for making me a recipe although I have heard it called a gene and sometimes they use three letters like NDA or AND or DNA.  I have also learned that the head librarian is not to be fooled with, and she has strict rules about not letting the original recipes out of the library.  However, she or someone else has figured out a clever copying process so that copies of the recipes can be taken out of the library to where ever they need to go.”

Protein Synthesis (According to Microbiology)

Before we get back to George’s training in waste disposal and his description of the trip that brought him to his plant, the first part of George’s tale needs to be translated into the terminology of protein synthesis in cells.

First George is a globular protein, more specifically a digestive enzyme that resides inside of lysosomes.  George correctly surmises that he is a chain of twenty kinds of links, which are the twenty amino acid residues that form all proteins. The original recipes kept in the library are the genes on the double helix strands of DNA in the cell’s nucleus.  George is aware that DNA is made of four kinds of links which are not amino acids and are called nucleotides.  The copy of the recipe, which is called the messenger, is the messenger RNA or m-RNA for short.  It leaves the nucleus and goes to a ribosome, or griddle as George describes it. The ribosome assembles the chain of amino acids which are brought to it by the “L-shaped guys” which are the transfer RNA’s or t-RNA for short. George has not figured out how each of the twenty amino acids are designated by the four nucleotides of DNA and RNA, but he correctly surmises that triplets of these are important.