Bill Dembski directs us to an article in Physics Today in which the authors say this:
Molecular machines are the basis of life. DNA, a long molecule that encodes the blueprints to create an organism, may be life's information storage medium, but it needs a bevy of machines to read and translate that information into action. The cell's nanometer-scale machines are mostly protein molecules, although a few are made from RNA, and they are capable of surprisingly complex manipulations. They perform almost all the important active tasks in the cell: metabolism, reproduction, response to changes in the environment, and so forth. They are incredibly sophisticated, and they, not their manmade counterparts, represent the pinnacle of nanotechnology. Yet scientists have no general theory for their assembly or operation.
How much can one molecule do? Consider, for example, ATP (adenosine triphosphate) synthase. This macromolecular assembly, only about 10 nanometers on a side, is an essential part of the cellular factory that produces ATP, the universal energy currency of life. We will not get into the details of the biological role of ATP synthase in the cell, but consider merely what it is capable of doing in isolation: It is a rotary motor. In the presence of a proton gradient, this remarkable machine turns a spindle as it adds phosphate groups to molecules of adenosine diphosphate to produce ATP. And every day the cells in your body perform this phosphate-addition reaction to produce roughly your body weight in ATP molecules.
But that is not all: ATP synthase can run in reverse. It can consume ATP, and with each ATP molecule that is hydrolyzed, the central shaft of ATP synthase turns by 120 degrees, directly converting chemical to mechanical energy. That reverse operation was explicitly demonstrated through a series of elegant experiments in which a molecular propeller was attached to the shaft and then imaged with optical microscopy.The propeller rotated in the presence of ATP, with absolute thermodynamic efficiencies of up to 90%. Despite the tremendous strides made in nanotechnology, no device of similar functionality can yet be fabricated with inorganic materials. Furthermore, many questions remain about the basic principles by which molecular machines such as ATP synthase convert chemical energy to mechanical forces.
After going on at some length in this vein the authors observe, in a masterful piece of understatement, that:
It is surely one of the triumphs of evolution that Nature discovered how to make highly accurate machines....
Note the difficulty of describing biological machines and information without using terms that are redolent of purpose:
One of the key hallmarks of biological function is ordering in space and time, and at least two great classes of biological orchestration should serve as a call to action for physicists: the coordination of physical structures and processes and the orchestration of information.
The whole article is worth reading but one passage in particular struck us. The authors write that:
Understanding collective effects in the cell will require merging two philosophical viewpoints. The first is that life is like a computer program: An infrastructure of machines carries out arbitrary instructions that are encoded into DNA software. The second viewpoint is purely physical: Life arises from a mixing together of chemicals that follow basic physical principles to self-assemble into an organism. Presumably, the repertoire of available behaviors is more limited in the latter. The two viewpoints are complementary, not incompatible: Either one could best describe cell behavior, depending on the particular situation.
Life is like a computer program, they tell us. If this is a legitimate analogy then we might ask if there has ever been a computer program which has come about through blind, purposeless forces and processes such as mutation and natural selection. It takes an enormous amount of blind faith in materialism to believe that something like a computer program could emerge purely by happenstance and physical forces, without any intelligent input, but no one should ever doubt the prodigious capacity for faith among Darwinians.
