DNA TO PROTEIN
Proteins are the basic building blocks of LIFE, making up the majority of the cellular structures and performing most life functions. Protein is Greek in origin meaning “primal life substance” Without proteins no living organisms would exist.
In understanding some of the functions of proteins and how they are created, you can begin to understand why the following statement explains, how proteins are not only fundamental to the creation of life, but addresses how well that life survives.
The altering or mutation of a gene, which results in the disruption in the function of a protein, can disrupt normal development or cause a medical condition.
To begin with we must associate the fact that all organic life is fundamentally created the same way. Organic is defined as: made up of systematically interrelated parts: organized. The opposite is inorganic: not having the organized structure of living things.
As discussed in the sections “The Cell” and the “The Genome,” each cell carries the complete instructions for creating the entire organism encoded in the DNA. The information contained in most genes produces proteins. Every cell contains thousands of different kinds of proteins, all with a specific function. In order for the cell to function correctly, each protein must perform their job at the right time and at the right place.
For example: the protein that makes up blood cells is called Hemoglobin. A gene whose job it is to create Hemoglobin proteins will create correctly functioning Hemoglobin proteins, if the gene (which is a sentence) is written accurately. Or transversely, if the sentence (gene) is corrupted (contains alterations or errors), the translation of the sentence will become corrupted and a poorly functioning or no protein at all may be created.
So how are proteins created?
Proteins are created in a systematically organized fashion, picture a production line in a factory. Each protein is made by stringing together a chain of amino acids. There are 20 amino acids that can be arranged into an infinite amount of sequences, creating a currently unknown number of proteins. Some proteins contain just a few amino acid combinations (chains), while more complex proteins contain 1000’s of amino acid combinations (chains) strung together.
The first step in creating a protein is to look up the instructions in the manual a.k.a the genome, for the specific protein you need to build. Once you have located the specific page where the information is written (the DNA), the next step is to make a photocopy of the instructions. The photocopying machine in cells is called the mRNA (messenger RNA.) By photocopying the information you keep the original information intact for the next time you need it.
The messenger RNA carries the photocopied instructions to a two-part molecular machine called the Ribosome. The photocopy is fed through the Ribosome which reads (translates) each word into one of the 20 amino acids. Next in the process comes the assembling or building of the protein… this is the job of the tRNA. As each word is translated, the tRNA transports, from other parts of the cell, the requested amino acid back to the Ribosome. Each amino acid is attached to the preceding amino acid forming a long chain. When the ribosome gets to a period (a stop) it releases the now complete protein.
After being released the protein is guided to a molecular machine that folds the protein to give it its precise shape. Amino acids come in a variety of shapes, the protein takes up its shape from the sequence of amino acids. The protein is now ready to go out into the cell and perform its specific role.
How does a cell know which protein to create?
I stated earlier that each cell contains the complete set of instructions for creating the entire organism; stated another way, each cell has the complete set of instructions for building every protein needed to create life. So how does each cell know when and which gene (instructions) to use to create only the proteins it needs. A blood cell for example needs to produce a hemoglobin protein, but a liver cell does not.
The process of using the information for creating a protein is called gene expression. It is also described as when a gene is switched “on” or is switched “off.” What switches genes “on” or “off”? Proteins! The genes that create these specific proteins are known as promoter genes (meaning to bring about.)
The job of these proteins is to either hide or expose the information from the complete manual, for building the specific proteins needed by a particular cell. View it this way; you have a manual describing how to build all the working components of a car, the person who’s job it is to build the piston doesn’t need all the information from the manual, so you hand over only the page which explains how to build the piston. This eliminates or reduces the risk of the wrong information being used resulting in a poorly or non functional piston being created.
What are all the functions of proteins?
As stated earlier, without proteins, no living organisms would exist. While it is impossible here to list every protein (we don’t even know of all of them), below are listed the categories of proteins, a few specific proteins and some of the functions they perform.
Structural proteins: the type and shape of proteins give cells their shape and help them move. Collagen is the most abundant structural protein and is a main component of the connective tissue. Keratin is used to create hair and skin and fibrin is deposited around a wound after an injury.
Enzymes: are proteins which make new molecules and catalyze (initiate) nearly all chemical processes in cells that lead to a particular function. Without enzymes controlling the process, there would be no order and chaos would ensue.
Hormones: are proteins which transmit signals throughout the body. Insulin, for example, plays a key role in regulating the amount of glucose in the blood. The body is made of trillions of individual cells. If cells were unable to talk and coordinate amongst themselves, complex life could not exist.
Antibodies: are proteins that recognize foreign molecules and destroy them. Foreign molecules are called antigens such as bacteria and viruses that have entered the body and could potentially be harmful. Our antibodies recognize an antigen by its protein structure. This is the basis for allergies; a very simple explanation of an allergy is our antibodies believing a usually harmless protein to be dangerous and so attacks it.
Transport proteins: Examples include lipoprotein which transports fat and cholesterol in the blood and hemoglobin which carries oxygen in the blood.
Storage Proteins: Examples include ovalbumin and casein. Ovalbumin is found in egg whites and casein is a milk-based protein these proteins store amino acids.
The genetic code carried by DNA is what specifies the order and number of amino acids and, therefore, the shape and function of the protein.
It is estimated that the human body may contain over 200,000 proteins. All organisms contain a Genome which produce proteins, in all organisms it is probably exceeds tens of millions of unique proteins, but no one really knows for sure.
When you consider that proteins are the basic building blocks of all life, the mere fact that we know so little is a big clue to the complexity of how life is created.
Scientists have made great advances in understanding the human genome, however, far less is understood and known about the “Proteome,” which is the name is given to describe the collection of proteins in a cell.
“Unlike the relatively unchanging genome, the dynamic proteome changes from minute to minute in response to tens of thousands of intra- and extra cellular environmental signals. A protein’s chemistry and behavior are specified by the gene sequence and by the number and identities of other proteins made in the same cell at the same time and with which it associates and reacts. Studies to explore protein structure and activities, known as proteomics, will be the focus of much research for decades to come and will help elucidate the molecular basis of health and disease.”The Human Genome Program of the U.S. Department of Energy Office of Science
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