Casey Luskin's recent Bio-Mechanics article in Salvo magazine offers a riveting and clear explanation of how molecular machines in the living cell point to intelligent design. Here are some excerpts with comments, and links to a few animations that illustrate the points even better than Luskin's still graphics.
Luskin writes (I've omitted the footnotes):
Molecular machines are ubiquitous in all living organisms. A 2004 article defined them as "devices that can produce useful work through the interaction of individual molecules at the molecular scale," and noted that "countless such machines exist in nature." Likewise, a paper in Nature Methods observed that "most cellular functions are executed by protein complexes, acting like molecular machines." One individual research project reported the discovery of over 250 new molecular machines in yeast alone.
Molecular machines use components we commonly recognize in human machinery. They may have joints, gears, propellers, turnstiles, brakes, and clutches, which form motors, tweezers, vehicles, assembly lines, transportation networks, intelligent error-checking systems, and much more.
The mechanical-technological terms used to describe tiny life-enabling devices in the living cell are not a wide stretch of metaphorical imagination. Living cells have thousands of such devices that actually exceed the energy efficiency ratings of most human technology. The next excerpt address this startling discovery.
But biomolecular machines have a major difference that distinguishes them from human technology: their energetic efficiency dwarfs our best accomplishments. One paper observes that molecular machines "are generally more efficient than their macroscale counterparts," and another suggests that the efficiency of the bacterial flagellum "could be [virtually] 100%." Human engineers can only dream of creating such devices
Although design theorist Michael Behe is especially famous for writing about the design implications of the bacterial flagellum (an outboard rotary engine attached to the cell membrane of many types of bacteria), this is just one of many, many examples throughout the biological world of single-celled and multicellular creatures.
Molecular machines also pose a stark challenge to Darwinian evolution. In Origin of Species, Darwin famously stated that, "If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down."
Because molecular machines cannot perform their functions until many parts are present and coordinated, they cannot be built by the "numerous, successive, slight modifications" required by Darwinian evolution. As Behe notes, "The complexity of life's foundation has paralyzed science's attempt to account for it; molecular machines raise an as-yet impenetrable barrier to Darwinism's universal reach."
Stephen Meyer explains this well to high school and college age students in TrueU: Does God Exist?
Luskin gives three examples of molecular machines, one of which is the ATP synthase device.
The ATP Synthase: This is a molecular machine that works like a rotary engine. It has many parts we recognize from human technology, including a rotor, a stator, and a camshaft. The machine's basic purpose is simple but vital for all life forms: it produces adenosine triphosphate (or ATP)—the energy molecule used by living cells to drive many biochemical reactions.
Watch this Animation of ATP Synthase in Action (hosted by the Department of Biochemistry at the Albert Einstein College of Medicine at Yeshiva University) with one browser window open while you read my description below. Then read Luskin's more detailed account in the Salvo article (Luskin's illustration is oriented upside down relative to the animated version).
Here is my description of the ATP synthase animation:
The barrel-shaped component at the bottom, powered by protons, spins around in order to transmit mechanical energy through a driveshaft that connects with the top component. The top component has parts that open and close in response to the periodic spin pulses of the irregularly shaped portion of the driveshaft (like a camshaft in a car engine as animated here). When (in the ATP synthase animation) the light purple and dark purple subunits are pushed open, spent-energy molecules called adenosine diphosphate (ADP), enter the machine. The mechanical motion of the ATP synthase machine causes an additional phosphate group to join with the ADP, creating ATP, which has 3, instead of just 2 phosphate units. The ATP made in this manner is released in the next part of the cycle of this ATP synthase machine.
This is a great way to simply "see" the effects of intelligent design. For a robust scientific argument for ID based on molecular machines see Michael Behe's Darwin's Black Box after you read Luskin's Bio-Mechanics article excerpted above.