Biological Structure and Reproduction
A cell nucleus contains deoxyribonucleic acid (DNA). DNA is a long-chain molecule composed of certain atomic structures called nucleic acids. These are arranged like a twisted ladder, a spiral staircase, or like the mating teeth on a long, winding zipper. The sequence of nucleic acids is the genetic code.
The structure is stable most of the time. But when the cell is reproducing itself, an enzyme partly unzips the DNA in the middle of a strand. It acts like the kind of zipper that one can open in the middle by moving two zipper sliders in opposite directions. Another enzyme reproduces one of the unzipped strands of DNA. It makes a new mating half for that strand. When the mating half is finished and floating away free inside the cell, the first enzyme zips up the original DNA again. Then other enzymes make a matching half to the floating half strand, and zip the two halves up. At the end of the process there are two zipped zippers instead of one.
The new zipper or DNA strand moves away from the original DNA strand to the far end of the cell. The cell is then ready to pinch itself in the middle and divide in two, with one DNA strand going to each half. This is the normal method of cell reproduction.
The two strands of zipped-up DNA are identical, because only certain pairs of nucleic acids interlock precisely to make the teeth of the zipper. In this way a cell makes a precise copy of its own genetic information before it divides and reproduces.
Once a cell reproduces it has to grow. Other enzymes read the relevant sections of the DNA code in the nucleus and provide instructions for manufacturing all the enzymes the cell needs. These enzymes produce all the proteins of the cell and all the molecules needed to digest food.
Enzymes all by themselves are fragile. Some enzymes must be kept on ice or they will denature. How then can they operate in living organisms at body temperature? Part of the requirement for life is the ability of the structure to maintain itself. When part of the maintenance system goes down, the whole organism collapses and dies. At the moment of death it still has most of the structure necessary for life, if only the broken part could be repaired quickly. However, within minutes thermal agitation disrupts the delicate coiling or folding of proteins that makes some of them active as enzymes. The enzymes denature and cannot catalyze the necessary chemical reactions. The structures they were maintaining then break down, and death becomes irreversible. It takes large systems of enzymes to maintain life.
Engineering is still far from miniaturizing its information storage and retrieval systems to the molecular level, or manufacturing such tiny robots as the enzymes in living cells.
The structure is stable most of the time. But when the cell is reproducing itself, an enzyme partly unzips the DNA in the middle of a strand. It acts like the kind of zipper that one can open in the middle by moving two zipper sliders in opposite directions. Another enzyme reproduces one of the unzipped strands of DNA. It makes a new mating half for that strand. When the mating half is finished and floating away free inside the cell, the first enzyme zips up the original DNA again. Then other enzymes make a matching half to the floating half strand, and zip the two halves up. At the end of the process there are two zipped zippers instead of one.
The new zipper or DNA strand moves away from the original DNA strand to the far end of the cell. The cell is then ready to pinch itself in the middle and divide in two, with one DNA strand going to each half. This is the normal method of cell reproduction.
The two strands of zipped-up DNA are identical, because only certain pairs of nucleic acids interlock precisely to make the teeth of the zipper. In this way a cell makes a precise copy of its own genetic information before it divides and reproduces.
Once a cell reproduces it has to grow. Other enzymes read the relevant sections of the DNA code in the nucleus and provide instructions for manufacturing all the enzymes the cell needs. These enzymes produce all the proteins of the cell and all the molecules needed to digest food.
Enzymes all by themselves are fragile. Some enzymes must be kept on ice or they will denature. How then can they operate in living organisms at body temperature? Part of the requirement for life is the ability of the structure to maintain itself. When part of the maintenance system goes down, the whole organism collapses and dies. At the moment of death it still has most of the structure necessary for life, if only the broken part could be repaired quickly. However, within minutes thermal agitation disrupts the delicate coiling or folding of proteins that makes some of them active as enzymes. The enzymes denature and cannot catalyze the necessary chemical reactions. The structures they were maintaining then break down, and death becomes irreversible. It takes large systems of enzymes to maintain life.
Engineering is still far from miniaturizing its information storage and retrieval systems to the molecular level, or manufacturing such tiny robots as the enzymes in living cells.
