Natural Nanomachines !
Summary
Your body is teeming with a natural form of nanotechnology, without which life as we know it is impossible.
Billions of years prior to the arrival of humankind, the world was—and continues to be—inhabited by hyper-advanced nanotechnology. Even today, in the age of supercomputers, material science, and robotics, the human brain has been unable to create anything as sophisticated as the nanomachines, called enzymes, permeating every cubic centimeter of biological tissue.
Enzymes are found in each of your trillions of cells and they literally rearrange the atoms making up certain molecules, transforming them into different molecules. Technically, enzymes are “catalysts”, meaning they allow some specific chemical reaction to proceed using less energy than would otherwise be required. This is true, but does not capture the wonder of these molecular workhorses.
Take a relatively simple enzyme, “proteinase K”, a protein which is able to cut other proteins to bits (a nice piece of nanoweaponry for a microorganism that wants to destroy its enemies and competitors). Humans, however, have isolated this nanoweapon from the microorganisms in which it evolved (a species of fungi (1)) and molecular biologists use it to destroy proteins in order to isolate DNA from samples of biological tissue.
Proteinase K works by slicing the bonds between the molecular units (amino acids) that make up all proteins; rather like freeing two arrestees handcuffed together by cutting the chainlinks joining their wrists. This is accomplished by proteinase K wrapping around a stretch of the amino acid chain that makes up the protein to be degraded, thereby positioning those amino acids in a pocket of the enzyme. Proteinase K then uses what biochemists call the “serine protease catalytic triad” to chemically separate one amino acid from its adjacent partner in a stepwise manner (2).
If you zoom in on the process, it is run of the mill chemistry. Yet, zooming out just a little, we see a pair of globular bolt cutters chopping links in a chain. This zoomed out view makes enzymes especially fascinating because these evolved entities come to resemble more familiar, human-made, tools.
Though proteinase K is derived from mold, human cells contain similar enzymes that use the same molecular mechanism. These enzymes have roles in digestion, wound healing, and other diverse processes (3). Such “serine proteases” are just one example of the abundant and wonderful phenomena of enzymes.
Other enzymes accomplish different tasks, like combining two molecules into one or extracting energy from the breaking of chemical bonds. These machines and their collective actions are largely what drive the happenings within and between biological cells. This means that everything you do, every action of your body, every thought or emotion instantiated in your brain, is possible thanks to the enzymatic nanomachinery humming in the molecular background.
One of the poetic truths uncovered by molecular biology is that every human body contains an inner galaxy of molecular complexity. We are energized by the air we breathe, constructed with the food we eat, and informed by the sensations we perceive; and all of these processes are carried out by billions of chemical reactions and microscopic physical interactions happening inside and among the cells that are involved in each.
The amazing thing is that this is all coordinated by evolved processes that result in particular sequences of molecular events in an organized network of many such events, resulting ultimately in an unified whole. In other words, when you put all this together in the right way, you get an organism behaving, sensing, and sometimes even thinking and feeling.
An example of a behavior could be as simple as cutting a chain with a pair of bolt cutters, in which case, curious observers might wonder what physical process within the person’s body caused him to move his muscles in that particular way. When they bothered to look, they would find simpler operations, like the hinging of joints and the contracting of muscle fibers, that explain what happened. If they looked closer, to the nanoscopic scale, they would find entities that, while certainly simpler, seem to be doing things and performing tasks of their own–perhaps resembling the bolt cutters as they cut the links in a chain of amino acids.
These observers would be justifiably astounded by the molecular bolt cutters because they would realize that these and other tiny machines are constantly working to keep the whole show going. These are the molecular workers churning out products for the cell, the salt of the biological Earth, the truly fascinating nanomachines known as enzymes.
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