Thursday, January 24, 2013

Cell Biology

When you start learning biology, there are new terms. With computers, your job, and/or your school, you learn new things all the time, so you are already acquainted with the activity. So I hope you will be open to learning about cell biology. It is a fascinating subject, and well worth the time. Perhaps you already know biology, but I hope you will still look at what I have here.

There are an estimated 75 trillion cells in the human body (and trillions of atoms in each cell). From bacteria to humans the cell is the basic unit of biology, and its activities are called “metabolism.” The cell absorbs and stores food, then breaks it down and converts it into energy. It uses energy to reproduce DNA (genes) and assemble proteins among other things. The DNA is used as a code for the proteins  which in turn do the work of the cell and the body. For example, your muscles have muscle cells which contain muscle proteins that contract and relax. They are called by specific terms, but we don’t have to name everything to get the overall perspective.

One of the basic parts of the ongoing process of metabolism is where several groups of proteins are embedded in a membrane of of the cell. The membranes are in folds, and in humans the folds are parts of what are called mitochondria (mite-oh-CON-dree-ah). First I have a short video (less than 4 minutes) for you to see how one of the groups works to form the energy molecule called ATP. ATP has chemical qualities that give it the ability to use a chemical bond for activity needed in the cell as I described above. It changes to ADP when used up, then is re-cycled back to ATP by this complex. You may hear some terms you don’t understand, but just try to get the concept of this series of steps going on in most of your body’s cells.

The video is done by North Dakota State University which has done other animations you can see here and here if you want to learn more. As interesting as the above video is, the protein complexes are drawn rather simply. Below is a more detailed picture of a series of complexes needed to make the last one, ATP Synthase (SIN-thase), work. They are needed to produce the electrical gradient which is described in the video. The mitochondrial membrane is pictured between the complexes, with ATP Synthase at the far right.

The picture comes from a database called Kegg, standing for Kyoto Encyclopedia of Genes and Genomes . The boxes in the picture give information for various parts of the complex when you click on them at the Kegg website.

Now, please stick with me a little longer to get more of the perspective of how complicated this series is. In the picture, the last group of proteins on the right is ATP Synthase. On the bottom part, there are blue-colored sections. The middle has a B on it for beta subunit (beta is Greek for “B”). Proteins are made of yet smaller units called amino acids (ah-ME-no acids). These are repeating groups of atoms, including carbon, oxygen, nitrogen and hydrogen (C, O, N and H). Here is a picture of one of the 20 types of amino acids found in biology, called alanine (AL-ah-neen):

The types of amino acids need to be in correct order, according to their size, electrical charge and other factors, so the proteins can fold into the shapes in which they function. It is similar to machine parts which need to have the right shapes to fit and move together. Now I have just one more picture. It is the list of amino acids in this one part of the whole complex, the beta (B) subunit of ATP Synthase as pictured above. This particular one (human) has 529 amino acids, as listed in another database called Uniprot . Each letter stands for an amino acid, such as A for alanine:

All the proteins parts of this entire complex are made of various arrangements of the amino acids. Many are at least 100 amino acids and some are many more, as you have seen. These need to be constructed and put together within most of the cells that we have. There are many such complexes within each cell.

Thank you for bearing with me to learn about this part of cell metabolism. Remember, this is only a very small fraction of the complexity in the cells. Even small organisms need energy systems such as these to put together their own genes and proteins. Please think about whether this could have come about by chance, no matter what the time frame. After all, a computer would not form on its own, no matter how many billions years pass, and that is not nearly as complicated as we are.

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