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Wetware: A Computer in Every Living Cell

Dennis Bray
Copyright Date: 2009
Published by: Yale University Press
Pages: 280
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  • Book Info
    Book Description:

    How does a single-cell creature, such as an amoeba, lead such a sophisticated life? How does it hunt living prey, respond to lights, sounds, and smells, and display complex sequences of movements without the benefit of a nervous system? This book offers a startling and original answer.

    In clear, jargon-free language, Dennis Bray taps the findings of the new discipline of systems biology to show that the internal chemistry of living cells is a form of computation. Cells are built out of molecular circuits that perform logical operations, as electronic devices do, but with unique properties. Bray argues that the computational juice of cells provides the basis of all the distinctive properties of living systems: it allows organisms to embody in their internal structure an image of the world, and this accounts for their adaptability, responsiveness, and intelligence.

    InWetware, Bray offers imaginative, wide-ranging and perceptive critiques of robotics and complexity theory, as well as many entertaining and telling anecdotes. For the general reader, the practicing scientist, and all others with an interest in the nature of life, the book is an exciting portal to some of biology's latest discoveries and ideas.

    eISBN: 978-0-300-15544-0
    Subjects: Developmental & Cell Biology, Biological Sciences

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
  3. Preface
    (pp. ix-xii)
  4. ONE Clever Cells
    (pp. 1-26)

    It was a rainy November Cambridge afternoon when Bill Grimstone appeared at my office in the Zoology Department and said he had something to show me. It was rare, even during the term, to sight him, and most unusual for him to be in such an animated state. Bill was an archetypal imperturbable Cambridge don: suave, phlegmatic, with graying hair, spectacles and a slight cast in one eye, and given to wearing a tweed jacket and a tie. As I followed him down the corridor to his room, I speculated that there could be only one reason for this excitement—...

  5. TWO Simulated Life
    (pp. 27-53)

    A strange form of life discovered tomorrow on a distant planet would transform biology. All of our notions of the origins of life are based on a single example, so it is impossible to tell which features are inevitable and which are historical accidents. Can you have a life form without DNA and proteins? Is it necessary to have large molecules made as polymers (chains) of smaller subunits to encode information and perform chemical tasks? Or might there be radically different solutions to the problems of growth and reproduction, perhaps employing a totally different chemistry . . . or no...

  6. THREE Protein Switches
    (pp. 54-70)

    A good place to start our descent to the realm of the very small is with thermal diffusion. This fundamental physical process dominates atoms and molecules and is crucial for all aspects of living cells. It is also an essential ingredient of wetware, providing the equivalent of connections, or wires, for the cell computer. Diffusion can be seen directly under a microscope and is something every biology student discovers afresh. You are examining tissue cells flattened on the surface of a plastic culture dish, or a drop of saliva on a slide. As you move the focus control up a...

  7. FOUR Protein Signals
    (pp. 71-88)

    Amoeba proteusis not one of those darling organisms like mice, fruit flies, andE. colithat have been chosen for in-depth analysis by molecular biologists. We have only a limited amount of information about its genes and proteins and mechanisms of motility. Giant amoebae have many special features such as streaming movements of their cytoplasm and a thick gel-like coating on their surface that are still incompletely explored. Moreover, even if we were fortunate in this respect and had a complete list of all the parts of an amoeba, we would still not be able to explain in detail...

  8. FIVE Cell Wiring
    (pp. 89-108)

    The difficulty with general principles in biology is that they are buried in a mountain of details. The theory of evolution came to Charles Darwin only after years of interest in natural history and an extended sea voyage that immersed him in a riot of natural variation. Biology’s most powerful generalization was distilled from a myriad of special cases, like alcohol from a mass of fermenting grain. Even today, although few scientists question the validity of Darwin’s theory, the way it operates can be subtle and hard to define.

    You can say the same about cellular computations. Although I’ve described...

  9. SIX Neural Nets
    (pp. 109-131)

    “Gug gah, bah bit,” the childish voice resonated in the elegant space of the Lady Mitchell Hall, a large lecture theater built for the University of Cambridge in the late 1950s. “Doo doo, wha woo” . . . an infant’s babble projected to an audience of perhaps three hundred academics, listening in solemn attention. The recording came from a laptop computer on a table, beside which sat a slim man in a dark suit, silently confronting the sea of faces before him. As we listened, the string of nonsense continued. What were we listening to? Then, unexpectedly . . ....

  10. SEVEN Cell Awareness
    (pp. 132-143)

    I am scribbling these notes seated on a hill in Scotland . . . one of those rare days on the West Coast when the clouds and mist roll away and the views have a crystalline clarity. Before me the Sound of Mull glints in the morning sun: wind-etched, steel-tempered blue. In the distance I see Ardnamurchan and the mainland, the Isles of Rhum and Egg, and farthest of all, the Cullins of Skye, like flat stage sets in shades of purple and gray. A cool wet wind blows in my face and whispers in my ears; a seagull flies...

  11. EIGHT Molecular Morphing
    (pp. 144-166)

    If responsiveness to the environment is an essential ingredient of all living forms, then logically it should have appeared at the same time as the first organisms. There are many debates about the origins of life. Even the location is uncertain, with some reputable scientists even suggesting that it may have occurred not on Earth but elsewhere in the solar system, or farther away. The precise sequence of chemical events that led to the creation of the first self-replicating entity may never be known, because no relics remain. But from our knowledge of present-day organisms, it is certainly possible to...

  12. NINE Cells Together
    (pp. 167-178)

    Robert Boyle, seventeenth-century scientist, was settling in for the night in his house in London when one of his servants informed him of a startling finding in the pantry. Apparently, a neck of veal purchased from a country butcher the week before had developed luminous patches of varying brightness and size.

    “They made a rather splendid show,” he wrote in a paper presented to the Royal Society on March 15, 1672. “In this one piece of meat I reckoned distinctly above twenty several places that did all of them shine, though not all of them alike, some of them doing...

  13. TEN Genetic Circuits
    (pp. 179-194)

    In the 1950s a group of biologists led by Jacques Monod and François Jacob working at the Institut Pasteur in Paris found thatE. colibacteria could use lactose, a sugar found in milk, as a source of food in place of the more usual glucose. In fact, within minutes of being transferred to a medium containing lactose as the only source of carbon atoms, the bacteria developed the enzymes and other molecules needed for its digestion. This was true even if the bacteria had never previously met lactose; they seemed to have an innate knowledge of this sugar, like...

  14. ELEVEN Robots
    (pp. 195-208)

    “And this is Lucy,” Steve announced, as I entered the workshop, stretching my legs after the long drive through the Somerset countryside. But before I could set down my bags and after the briefest of greetings, Steve Grand and his wife, Ann, waved me to the outbuilding. Situated to the right of their small house, set under one of the trees in their leafy garden, was a single-story outhouse, probably built as a large garage or perhaps a granny annexe. I entered a single spacious room, low-ceilinged and filled with workbenches. Electronic gear was everywhere—transistors, small motors, cogs, wires,...

  15. TWELVE The Juice
    (pp. 209-225)

    Estimates of the number of nerve cells in an adult human brain usually weigh in at around one hundred billion. That means 100,000,000,000 self-contained entities, each a molecular metropolis in its own right. (The number of supporting glial cells, which some experts believe contribute to learning and mentation, is five to ten times higher.) Nerve cells, or neurons, have a cell body containing the nucleus and numerous long, thin extensions. Usually, one long axon conducts signals away from the cell body toward distant target cells, and many shorter branching dendrites act like antennae or whiskers, collecting signals from other cells....

  16. THIRTEEN Amoeba Redux
    (pp. 226-242)

    I began this book with the movements of single cells, and perhaps that will be a good topic with which to finish. What can I now say about the predation of amoebae or the avoidance of stentor, given a better notion of how they work? How do these single-cell organisms operate in an integrated, apparently motivated fashion? Where does their sensibility come from? What can I say about their self-knowledge?

    The starting point is a cell stuffed full of molecules, especially proteins. Proteins provide the equivalent of muscles, skeleton, digestive system, and lungs. They create networks of communication and logical...

  17. Glossary
    (pp. 243-250)
  18. Sources and Further Reading
    (pp. 251-258)
  19. Index
    (pp. 259-267)