The Physics of God by Joseph Selbie

The Physics of God by Joseph Selbie

Author:Joseph Selbie
Language: eng
Format: epub
Publisher: Career Press
Published: 2018-01-13T05:00:00+00:00


FIGURE 8. The basic structure of DNA: two long chains of nucleic acids that coil around each other, forming a double helix as a result of the attraction of pairs of nucleic acids—adenine to thymine and cytosine to guanine.

Our cells are, to a large extent, protein factories. To produce a protein, first the DNA in the nucleus relaxes its tightly coiled double helix shape along a short segment of its full length (rather like twisting open and stretching out just a few coils in a long spring), thereby exposing a segment of the DNA strand that contains the coded blueprint for one particular protein. Once the DNA uncoils, another type of molecule (very similar to DNA, called messenger RNA or mRNA) begins to form, amino acid by amino acid, along one strand of the exposed DNA (Figure 9). The result is a new chain of amino acids that exactly matches the sequence of the DNA chain. Now a perfect copy of the sequence exposed by the DNA and a blueprint for a single protein, the mRNA “unzips” from the DNA and exits the nucleus.

Once it leaves the nucleus, the RNA is grabbed by a ribosome. Ribosomes, which are protein-making machines in the cell, connect together one amino acid after another in a long chain exactly matching the sequence coded in the RNA (Figure 10). As the chain lengthens, it folds upon itself, creating a distinct size and shape. Proteins can be made from hundreds or even thousands of amino acids connected together in an exact sequence. The protein, once created, is put to work in the cell’s structure, or in the cell’s processes (such as binding or catalyzing), or it is sent out of the cell to where it is needed for other life processes such as digestion or hormonal regulation.

Our cells are incredibly prolific protein factories. It takes only seconds for each ribosome to produce a finished protein molecule containing as many as several thousand amino acids. Each of our body’s cells can produce hundreds of thousands, even millions, of protein molecules in a single day; and each cell is theoretically capable of producing every one of the 20 million different proteins encoded in human DNA.



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