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Posted on 07/19/2009 5:42:44 PM PDT by SeekAndFind
To a physicist, life seems little short of miraculous — all those stupid atoms getting together to perform such clever tricks! For centuries, living organisms were regarded as some sort of magic matter. Today, we know that no special “life force” is at work in biology; there is just ordinary matter doing extraordinary things, all the while obeying the familiar laws of physics. What, then, is the secret of life’s remarkable properties?
In the late 1940s and 1950s it was fashionable to suppose that quantum mechanics — or perhaps some soon-to-be-formulated “post-quantum mechanics” — held the key to the mystery of life. Flushed with their success in explaining the properties of non-living matter, the founders of quantum mechanics hoped their theory was both weird enough and powerful enough to explain the peculiar living state of matter too. Niels Bohr, Werner Heisenberg and Eugene Wigner all offered speculations, while Erwin Schrödinger’s famous book What is Life?, published in 1944, paved the way for the birth of molecular biology in the 1950s.
Half a century later, the dream that quantum mechanics would somehow explain life “at a stroke” — as it had explained other states of matter so distinctively and comprehensively — has not been fulfilled. Undoubtedly, quantum mechanics is needed to explain the sizes and shapes of molecules and the details of their chemical bonding, but no clear-cut “life principle” has emerged from the quantum realm that would single out the living state as in any way special. Furthermore, classical ball-and-stick models seem adequate for most explanations in molecular biology.
In spite of this, there have been persistent claims that quantum mechanics can play a fundamental role in biology, for example through coherent superpositions and entanglement. These claims range from plausible ideas, like quantum-assisted protein folding, to more speculative suggestions, such as the one proposed by Roger Penrose of the University of Oxford and Stuart Hameroff of the University of Arizona that quantum mechanics explains consciousness by operating in the brain over macroscopic dimensions. Unfortunately, biological systems are so complex that it is hard to separate “pure” quantum effects from the shifting melee of essentially classical processes that are also present. There is thus plenty of scope for disagreement about the extent to which life utilizes non-trivial quantum processes.
But why should quantum mechanics be relevant to life, beyond explaining the basic structure and interaction of molecules? One general argument is that quantum effects can serve to facilitate processes that are either slow or impossible according to classical physics. Physicists are familiar with the fact that discreteness, quantum tunnelling, superposition and entanglement produce novel and unexpected phenomena. Life has had three and a half billion years to solve problems and optimize efficiency. If quantum mechanics can enhance its performance, or open up new possibilities, it is likely that life will have discovered the fact and exploited the opportunities. Given that the basic processes of biology take place at a molecular level, harnessing quantum effects does not seem a priori implausible.
Even if life does not actively exploit “quantum trickery”, we cannot ignore the impact of quantum mechanics on biology. Quantum uncertainty sets a fundamental bound on the fidelity of all molecular processes. A distinctive feature of biology is the exquisite choreography involved in its highly complex molecular self-organization and self-assembly. For the cell to perform properly, it is crucial that the right parts are in the right place at the right time. Quantum mechanics sets fundamental limits to the accuracy with which molecules can co-operate in a collective and organized way. We might expect some of life’s processes to evolve at least as far as the “quantum edge”, where a compromise is struck between speed and accuracy.
The 19th-century view of life as “magic matter”, exemplified by the use of the term “organic chemistry”, has been replaced by a model of the cell as a complex system of linked nanomachines operating under the control of digital software encoded in DNA. These Lilliputian components, made mostly from proteins, include pumps, rotors, ratchets, cables, levers, sensors and other mechanisms familiar to the physicist and engineer. Their exquisite design, honed by eons of evolution, exhibits extraordinary efficiency and versatility, and is an inspiration to nanotechnologists. Intuition gained from macroscopic and mesoscopic mechanisms can be misleading on a nano-scale, where quantum phenomena such as the Casimir effect could come into play and dramatically change the nature of the forces involved.
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There is accumulating and tantalizing evidence that quantum mechanics plays a key role here and there in biology. What is lacking is any clear case for a general “quantum life principle” that might offer a new conceptual framework in which the remarkable properties of living systems can be understood, as Schrödinger and others hoped. However, the physics of complex far-from-equilibrium quantum systems with non-linear couplings is in its infancy, and further surprises undoubtedly lie in store. Meanwhile, researchers in quantum-information science intent on reducing decoherence might find the study of biological nanomachines surprisingly rewarding.
Recent efforts to plug into DNA for the purpose of processing data or using it as a switching mechanism are leading the way.
“Today, we know that no special “life force” is at work in biology; there is just ordinary matter doing extraordinary things, all the while obeying the familiar laws of physics.”
Just like there are vast amounts of radio waves on Earth that don’t do anything. Carry data? Why, that would suggest that radio waves are intelligent. What nonsense! They just obey the familiar laws of physics.
His error is assuming that life and it life force are two different things. The human body clearly has energy, of several different kinds. How impossible would it be to think that this energy also carried data?
If I could only find someone who can explain quantum mechanics.
Quantum mechanics can not explain information-rich DNA, and more importantly, the meaning of codons and their associated amino acids.
Davies is an evolutionist?
Try Brian Greene, who gives a good explanation before going off into discussion of string theory, or Paul Davies, or Leon Lederman.
CELL.
A good start to learn QM is to follow this video course from India http://nptel.iitm.ac.in/video.php?courseId=1090
Balakrishnan is a very good teacher.
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