Teamwork for Life
Life could not exist on earth without the teamwork of protein and nucleic acid molecules (DNA or RNA) within a living cell. Let us briefly review some of the details of that intriguing molecular teamwork, for they are the reason why many find it hard to believe that living cells appeared by accident.
Peering into the human body, down to and even inside our microscopic cells, we find that we consist primarily of protein molecules. Most of these are made up of ribbonlike strips of amino acids that are bent and twisted into various shapes. Some fold into a ball, whereas others are shaped like accordion pleats.
Certain proteins work with fatlike molecules to form cell membranes. Others help carry oxygen from the lungs to the rest of our body. Some proteins act as enzymes (catalysts) to digest our food by splitting the proteins in the food into amino acids. Those are just a few of the thousands of tasks that proteins perform. You would be right in saying that proteins are the skilled workers of life; without them life would not exist. Proteins, in turn, would not exist were it not for their link with DNA. But what is DNA? What is it like? How is it linked with proteins? Brilliant scientists have won Nobel prizes for uncovering the answers. We, though, do not have to be advanced biologists to grasp the basics.
The Master Molecule
Cells are largely made of proteins, so new proteins are constantly needed to maintain cells, to make new cells, and to facilitate chemical reactions within cells. The instructions needed for producing proteins are contained in the DNA (deoxyribonucleic acid) molecules. To understand better how protein is produced, take a closer look at DNA.
DNA molecules reside in the cell nucleus. In addition to carrying instructions necessary for the production of proteins, DNA stores and transmits genetic information from one generation of cells to the next. The shape of DNA molecules resembles a twisted rope ladder (termed a "double helix"). Each of the two strands in the DNA ladder consists of a vast number of smaller parts called nucleotides, which exist in one of four types: adenine (A), guanine (G), cytosine (C), and thymine (T). With this DNA "alphabet," a pair of letters-either A with T or G with C-form one rung in the double-helix ladder. The ladder contains thousands of genes, the basic units of heredity.
A gene holds the information needed to build a protein. The sequence of letters in the gene forms a coded message, or blueprint, that tells what kind of protein should be built. Hence, the DNA, with all its subunits, is the master molecule of life. Without its coded instructions, diverse proteins could not exist-thus no life.
The Go-Betweens
However, since the blueprint for building a protein is stored in the nucleus of the cell and the actual site for building proteins is outside the nucleus, help is needed to get the coded blueprint from the nucleus to the "building site." RNA (ribonucleic acid) molecules provide this help. RNA molecules are chemically similar to those of DNA, and several forms of RNA are needed to do the job. Take a closer look at these extremely complex processes for making our vital proteins with the help of RNA.
Work starts in the cell's nucleus, where a section of the DNA ladder unzips. This allows RNA letters to link to the exposed DNA letters of one of the DNA strands. An enzyme moves along the RNA letters to join them into a strand. Thus DNA letters are transcribed into RNA letters, forming what you might call a DNA dialect. The newly formed chain of RNA peels away, and the DNA ladder zips up again.
After further modification, this particular type of message-carrying RNA is ready. It moves out of the nucleus and heads for the protein-production site, where the RNA letters are decoded. Each set of three RNA letters forms a "word" that calls for one specific amino acid. Another form of RNA looks for that amino acid, grabs it with the help of an enzyme, and tows it to the "construction site." As the RNA sentence is being read and translated, a growing chain of amino acids is produced. This chain curls and folds into a unique shape, leading to one kind of protein. And there may well be over 50,000 kinds in our body.
Even this process of protein folding is significant. In 1996, scientists around the world, "armed with their best computer programs, competed to solve one of the most complex problems in biology: how a single protein, made from a long string of amino acids, folds itself into the intricate shape that determines the role it plays in life. . . . The result, succinctly put, was this: the computers lost and the proteins won. . . . Scientists have estimated that for an average-sized protein, made from 100 amino acids, solving the folding problem by trying every possibility would take 1027 (a billion billion billion) years."-The New York Times.
We have considered only a summary of how a protein is formed, but you can see what an incredibly complex process it is. Have you an idea of how long it takes for a chain of 20 amino acids to form? About one second! And this process goes on constantly in our body cells, from our head to our foot and everywhere in between.
What is the point? While other factors too numerous to mention are involved, the teamwork needed to produce and maintain life is awe-inspiring. And the term "teamwork" hardly describes the precise interaction required to produce a protein molecule, since a protein needs information from DNA molecules, and DNA needs several forms of specialized RNA molecules. Nor can we ignore the various enzymes, each performing a distinct and vital role. As our body makes new cells, which happens billions of times a day and without our conscious guidance, it requires copies of all three components-DNA, RNA, and protein. You can see why the magazine New Scientist comments: "Take away any one of the three and life grinds to a halt." Or take this a step further. Without a complete and functioning team, life could not have come about.
Is it reasonable that each of those three molecular team players arose spontaneously at the same time, in the same place, and so precisely tuned that they could combine to work their wonders?
There is, though, an alternative explanation as to how life on earth came about. Many have come to believe that life was the careful product of a Designer with intelligence of the highest order.
Life could not exist on earth without the teamwork of protein and nucleic acid molecules (DNA or RNA) within a living cell. Let us briefly review some of the details of that intriguing molecular teamwork, for they are the reason why many find it hard to believe that living cells appeared by accident.
Peering into the human body, down to and even inside our microscopic cells, we find that we consist primarily of protein molecules. Most of these are made up of ribbonlike strips of amino acids that are bent and twisted into various shapes. Some fold into a ball, whereas others are shaped like accordion pleats.
Certain proteins work with fatlike molecules to form cell membranes. Others help carry oxygen from the lungs to the rest of our body. Some proteins act as enzymes (catalysts) to digest our food by splitting the proteins in the food into amino acids. Those are just a few of the thousands of tasks that proteins perform. You would be right in saying that proteins are the skilled workers of life; without them life would not exist. Proteins, in turn, would not exist were it not for their link with DNA. But what is DNA? What is it like? How is it linked with proteins? Brilliant scientists have won Nobel prizes for uncovering the answers. We, though, do not have to be advanced biologists to grasp the basics.
The Master Molecule
Cells are largely made of proteins, so new proteins are constantly needed to maintain cells, to make new cells, and to facilitate chemical reactions within cells. The instructions needed for producing proteins are contained in the DNA (deoxyribonucleic acid) molecules. To understand better how protein is produced, take a closer look at DNA.
DNA molecules reside in the cell nucleus. In addition to carrying instructions necessary for the production of proteins, DNA stores and transmits genetic information from one generation of cells to the next. The shape of DNA molecules resembles a twisted rope ladder (termed a "double helix"). Each of the two strands in the DNA ladder consists of a vast number of smaller parts called nucleotides, which exist in one of four types: adenine (A), guanine (G), cytosine (C), and thymine (T). With this DNA "alphabet," a pair of letters-either A with T or G with C-form one rung in the double-helix ladder. The ladder contains thousands of genes, the basic units of heredity.
A gene holds the information needed to build a protein. The sequence of letters in the gene forms a coded message, or blueprint, that tells what kind of protein should be built. Hence, the DNA, with all its subunits, is the master molecule of life. Without its coded instructions, diverse proteins could not exist-thus no life.
The Go-Betweens
However, since the blueprint for building a protein is stored in the nucleus of the cell and the actual site for building proteins is outside the nucleus, help is needed to get the coded blueprint from the nucleus to the "building site." RNA (ribonucleic acid) molecules provide this help. RNA molecules are chemically similar to those of DNA, and several forms of RNA are needed to do the job. Take a closer look at these extremely complex processes for making our vital proteins with the help of RNA.
Work starts in the cell's nucleus, where a section of the DNA ladder unzips. This allows RNA letters to link to the exposed DNA letters of one of the DNA strands. An enzyme moves along the RNA letters to join them into a strand. Thus DNA letters are transcribed into RNA letters, forming what you might call a DNA dialect. The newly formed chain of RNA peels away, and the DNA ladder zips up again.
After further modification, this particular type of message-carrying RNA is ready. It moves out of the nucleus and heads for the protein-production site, where the RNA letters are decoded. Each set of three RNA letters forms a "word" that calls for one specific amino acid. Another form of RNA looks for that amino acid, grabs it with the help of an enzyme, and tows it to the "construction site." As the RNA sentence is being read and translated, a growing chain of amino acids is produced. This chain curls and folds into a unique shape, leading to one kind of protein. And there may well be over 50,000 kinds in our body.
Even this process of protein folding is significant. In 1996, scientists around the world, "armed with their best computer programs, competed to solve one of the most complex problems in biology: how a single protein, made from a long string of amino acids, folds itself into the intricate shape that determines the role it plays in life. . . . The result, succinctly put, was this: the computers lost and the proteins won. . . . Scientists have estimated that for an average-sized protein, made from 100 amino acids, solving the folding problem by trying every possibility would take 1027 (a billion billion billion) years."-The New York Times.
We have considered only a summary of how a protein is formed, but you can see what an incredibly complex process it is. Have you an idea of how long it takes for a chain of 20 amino acids to form? About one second! And this process goes on constantly in our body cells, from our head to our foot and everywhere in between.
What is the point? While other factors too numerous to mention are involved, the teamwork needed to produce and maintain life is awe-inspiring. And the term "teamwork" hardly describes the precise interaction required to produce a protein molecule, since a protein needs information from DNA molecules, and DNA needs several forms of specialized RNA molecules. Nor can we ignore the various enzymes, each performing a distinct and vital role. As our body makes new cells, which happens billions of times a day and without our conscious guidance, it requires copies of all three components-DNA, RNA, and protein. You can see why the magazine New Scientist comments: "Take away any one of the three and life grinds to a halt." Or take this a step further. Without a complete and functioning team, life could not have come about.
Is it reasonable that each of those three molecular team players arose spontaneously at the same time, in the same place, and so precisely tuned that they could combine to work their wonders?
There is, though, an alternative explanation as to how life on earth came about. Many have come to believe that life was the careful product of a Designer with intelligence of the highest order.
