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Quantum mechanics, life’s motive force?

Nature isn’t classical

‘Nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical, and by golly, it’s a wonderful problem, because it doesn’t look so easy.’ ~ Richard P. Feynman, Ph.D.

Well, all right, Professor Feynman. Quantum it shall be. As you say, it’s not so easy. Many answers beyond our imagination hide beneath a layer, or many layers of Nature, we have yet to reach. Perhaps we never will.

Children admire butterflies’ wing markings, wondering: ‘Why do they have such pretty designs?’ and, ‘How do they get the patterns to match on both sides?’ Patterns and colours reflect from one side to another, exactly. Perfect symmetry comes under the heading of ‘How’. How is a much more complicated tale than why.

Eggs change to adults. Eggs become adults. Many insects go through several shifts in form—egg, caterpillar, pupa, adult butterfly. This involves rearranging the very setup of the creature’s flesh at each stage, until the thing is mature. (Blog: Of Potter’s Clay and DNA).

How to describe this far-from-little miracle? It’s not easy. The process is easier to follow in ancient worms.

Before the Cambrian explosion of life cast a jungle of new, multi-celled species into the oceans, the genetic makeup of ancestral worm-like creatures consisted of undifferentiated cells, which is to say identical, and therefore unspecialised.

An adult Caenorhabditis elegans nematode, stained. (Quantum)

A Caenorhabditis elegans nematode, stained.   Credit: Siegfried Hekimi

DNA may come to Nature’s hand either fresh (as undifferentiated genetic material), or as genes that have already shaped proteins, organs, limbs, appendages and sinews in untold species that took forms along life’s very long road. That said, questions about butterflies’ wings  beguiling children also teased geneticists through much of the twentieth century. How does a creature develop from identical larval cells into a coherent body in which cells become specialized and take on many different functions and forms? Before they can do that, each cell has to move, or be moved, through the mass of other jostling cells. Only when a cell is appropriately placed in what will become a defined, final body—only then can a cell be ordered to become the component it is destined to be, as bone, kidney, nerve, blood or flesh. Here’s how it happens.

Quantum, and the humble nematode

Much-studied nematode worms reveal some of Nature’s mechanics for sculpting eggs into organisms. Millimeters long, nematodes—nema, ‘thread’ in Greek—are common beyond number in water, soil and mud. Many species are transparent, so it is easy to watch a fertilized egg divide—two cells into four, four into eight, eight to sixteen …

At first, each undifferentiated cell in the rapidly dividing mass is identical to its fellows in every respect. Under a microscope, even as the cells are dividing and multiplying, each tiny, undifferentiated cell is seen jostling its way through the others—all of them jostling through the crowd, until each one reaches a destination ‘designated’ by an unknown force. Under a microscope it is clear that each undifferentiated cell ‘knows’ where it is supposed to go, even if it may not yet ‘know’ which bodily organ it will join. (The visual effect is not unlike looking down on a human crowd at a busy station in rush hour, seeing each person struggle through the mass in order to reach a personal destination.)

Following their mass migration, each re-positioned cell abandons its undifferentiated youth and becomes whatever the embryo nematode’s grand plan needs it to be: part of a mouth, a lining in the gut wall, skin … Eleven hours after their first division, the first two undifferentiated cells of a fertilized egg have become 558 specialized cells of a perfectly formed nematode, ready to hatch.

What moves these cells?

What moves these cells to their positions? A cell steers its course through its crush of neighbors because sensors in its surface detect chemical conditions around it and respond accordingly. Meanwhile, the several hundred other cells in the scrum are squeezing their way to their own destinations.

How can that happen? Cell-surface sensors act as electrochemical guide dogs, directing their cell through the jostling throng. By so doing, these cell-surface sensors send the mass of undifferentiated cells to their eventual places, where they are predestined (?) to play a specialized role in the final organism.

Research reveals how cell-surface sensors work. A cell’s outer wall is made of a double layer of lipid, or fat. Specific protein molecules ‘float’ in this fatty membrane. These proteins include sensors, perhaps several thousands of them in the surface of each cell.

One type is known as an ion channel. Under a microscope these resemble tiny pores in skin. The ion channels allow electrically charged particles—ions—through the membrane, into or out of a cell. An ion channel reacts to an external stimulus by opening to let appropriate ions pass into the cell from the environment. Some channels pass sodium ions, others pass calcium or potassium ions, and so on.

Since the surface of each cell houses several thousand ion channels, the amount of electro-chemical ‘sensory’ data informing any one cell is vast. Each cell gains a sensory ‘general positioning’ of its location with respect to the external environment, and the relative positions of cells around it. At some point an embryonic cell must also become aware of the fate of the cells around it—what will they become?—in order to move to, and take up, its own correct place in the organic jigsaw puzzle.  So, each undifferentiated cell seems to ‘recognise’ where it is supposed to end up relative to its fellows in the scrum. Imagine a jigsaw puzzle accurately assembling the bits of itself.

These cell-surface sensors, protein molecules billionths of a meter long, sample the electro-chemical data guiding cells into place as components in specific beings. Will a given cell become part of a mouth, or a gut? The fate of each embryonic cell is coded in the molecular language of nanospace.

Masahiro Sukabe

Masahiro Sukabe. Photo: MechanicoBiology Institute, National University of Singapore.

At Nagoya University, Masahiro Sokabe has isolated individual ion channels to discover how they work. Applying pressure or electrical stimuli, Sokabe records responses from individual channels, monitoring their ionic flows by computer. He knows when a channel opens, and when it closes again. In short, Sokabe can tell when a cell-surface sensor is accepting or rejecting electro-chemical stimuli from the outer world. [1]

Sokabe comments that his work records ‘a record of awareness, not of a cell, but of one sensor on the surface of a cell. A sensor is aware. Its channel opens to admit external influences, and closes again at intervals of about one one-thousandth of a second.’ Musing, Sokabe adds, ‘An ion channel behaves like a computer gate: it is either open, or closed.’

With perhaps one thousand cell-surface sensors commanding every possible electrolyte to either ‘stop’ or ‘go’ at a rate of one thousand times a second, each of the 558 cells in a larval nematode is well informed: at that rate, the total number of biochemical data samplings within the tiny, developing worm reaches 558 million per second. ‘It’s clear that the channel molecules are behaving almost digitally,’ says Sokabe. ‘Each cell is doing complex calculations on information it gets from the world around it. Based on the results it gets, it moves, it secretes a hormone or responds to a stimulus. We consider a cell—each single cell—to be working like a very complex computer.’ Nature devised this biochemical process to enable multi-celled animals to build life.

Our recent computer age finds us treading through fields of vast numbers. Our experience with such numbers is becoming a sort of pastoral address on the infinite ways of Nature.

Advanced mathematics has been tying itself in knots for decades to solve an equation that is written: m = p x q. This has something to do with large prime numbers—that’s all I know. My point is, in order to solve this problem:

Think of the enormous number of sensors simultaneously working in cell membranes of a maturing worm. Nature has been functioning at quantum proficiency in multi-celled creatures since their beginning.

One more point: Ask a standard computer to thread a course through a complex maze and it will try one route at a time. Ask a quantum computer to try the same thing and it will probe 64 possible routes at once. So, how does a larval cell shoulder its way, 1/ through the crush of its fellows?  2/ through an organic maze?  3/ and what decides its destination? We know that larval cells migrate to become their final creature: we think we understand that at the level of single molecules and charged particles. Some force endows living cells with an almost quantum quality.

Horizontally Influenced Depth-First Search Generated Maze

Horizontally Influenced Depth-First Search-Generated Maze. Created: 21 February 2014 Ofek Gila, English Wikipedia. CC BY-SA 3.0

What drives this life-force?

 The unanswered question remains: what  directs this life-force? What force, what architect draws the map, generates the impulses and plans the destinations?

Physicist Richard Feynman brought us into this fine mess. Let’s let him take us out:

‘If you think you understand quantum mechanics, you don’t understand quantum mechanics.’

No. However, let’s take one thing at a time. Perhaps we should try to understand our life-force first.

• • •

Copyright Robert Fripp 2002, 2017. This post is based on a chapter in my book, Let There Be Life, (Paulist Press, HiddenSpring Imprint, 2002). It is not in the earlier U.K. version, The Becoming.

[1] The Japan Broadcasting Corporation, NHK, produced a three-part television series, Nanospace, about the worlds of very small things. Among other awards, Nanospace won the prestigious Prix Leonardo (1993) for the best science television documentary. Part II describes Professor Sokabe’s work with nematodes. I versioned the Nanospace series into English.

An interesting quantum page: ibm.com/IBMQ