Biochemistry Professor, Michael Behe of Lehigh University (Penn, USA) was one of the first public proponents of the concept of ‘irreducible complexity’.

All at once or not at all

In his book “Darwin’s Black Box”, he provides a number of examples of the way in which many biological systems are too complex at the molecular level to be explained by evolution. He shows that these systems had to be created complete because they won’t work at a more simple level. Behe uses the example of the mousetrap to explain that complex molecular systems cannot evolve in Dawinian fashion. He explains:

“You can’t start with a platform, catch a few mice, add a spring, catch a few more mice, add a hammer, catch a few more mice, and so on. The whole system has to be put together at once or the mice get away.”

Interestingly, Behe’s book has inflamed passion amongst a number of prominent scientists. Curiously, his work is usually criticised on the basis of a lack of peer review than factual error. An ‘open letter’ still circulates on the web from one of my ex-scientist colleagues rudely accusing Behe of virtually being a fraud.

The cell shows at many different levels the fact that the systems that keep it functioning had to be created all at the same time. It is not possible to create the many super complex functions of the cell by progressive improvements.

Cellular shipping

One of the functions which illustrates this is cellular transport. In the most simple sense, cells consist of a membrane which house a number of ‘organelles’ which are in turn all enclosed by membranes. The organelles (all of which have exotic names) are

vol 14 - 6

equivalent to the organs of the human body. For example there are organelles which satisfy the energy requirements of the cell (mitochondrion), others that produce new proteins (endoplasmic reticulum), and others which are used for storage (vacuoles).

These membranes keep the distinct functions of the cell separate, that is, the waste disposal functions of the cell are kept separate from the energy producing functions, just as the bathroom of a house is kept separate from the kitchen. These barriers between organelles would ordinarily prevent the passage of ‘supplies’ into the cell and the egress of waste out of the cell. However, God in His wisdom has designed a transport system that allows the greatest efficiency possible even at a microscopic level. To prevent each organelle of the cell having to manufacture everything it needs to remain functioning, the majority of materials required are manufactured centrally and then shipped to the target organelle.

vol 14 6

Parcel post

If you consider the transport of protein from one organelle to another the distances involved are  miniscule. The distance travelled from one organelle  to another is typically less than 0.0025mm. It  is worth considering the complex molecular technology that is required in order to undertake vesicular transport across these microscopically  small distances.

Almost everything that is shipped out of the cell is a peptide or a protein. Very broadly speaking there are 2 main[1] transport routes in and out of the cell. These are gated transport and vesicular transport.

Gated transport

In cases where gated transport is utilised, a passage in the cell wall opens up, the protein passes through and the gate closes again afterwards. There are  many different types of ways in which the gate  on the channel through the membrane can work  – it could be activated by a change in voltage or energy states, or a simple change in shape. In the figure (right) we have illustrated the way in which  a change in the shape of the protein spanning the membrane of the organelle can transport glucose into the cell. Similar mechanisms act to transport  small molecules and peptides / proteins out of the  cell or organelle.

The bare essentials of gated transport are threefold:

  1. An ID tag (think ‘barcode’) is required on the protein to be transported to uniquely identify it
  2. A scanner is required on the transporter Protein
  3. A gate that is activated by the scanner.

As Behe notes in his book, “because gated transport requires a minimum of three separate components to function, it is irreducibly complex”. In other words, all of these components had to have been created simultaneously to create a functioning mechanism. If the channel through the membrane existed in isolation, proteins could constantly leak out of the organelle. If the proteins didn’t contain any ID tag, there would be no way of identifying which proteins needed to be transported. The same is true if the protein scanner was missing.

Vesicular transport

Vesicular transport involves the use of a shipping container called a ‘vesicle’. These ‘membranous  sacks’ form when a section of the cell membrane ‘invaginates’ and ‘buds off’. If you look at the way that vesicular transport works it has a number of requirements, most of which are common to any  kind of freight movement:

vol 14 7

  1. As for gated transport, an ID tag is required on the protein to be transported
  2. A scanner is required on the vesicle to detect the protein to be transported
  3. A vesicle (think ‘shipping container’) is needed to transport the protei
  4. An ID tag (barcode) on the vesicle is also Needed
  5. A scanner on the surface of organelle 2 is Necessary
  6. A delivery mechanism is required.

Because vesicular transport is so much more complicated than gated transport it cannot just  ‘develop’ from this simpler system. These are completely different transport mechanisms. Understanding one doesn’t aid understanding of the other. Even if gated transport did happen to evolve, there is no logical progression from this to vesicular transport. If vesicles had just evolved without any of the other mechanisms involved in this transport process, then the whole system would be completely dysfunctional. There would be no way of identifying the proteins to pack into the vesicles and no way of sending the vesicle to the correct destination. Even if by chance a system of placing an ID tag on a protein developed and the correct proteins were packed into a vesicle –  without any means of sending these proteins to their correct location they would never unpack and would ceaselessly circle the cell.

This is an exceptionally brief explanation of a highly complex biochemical pathway that fails to take into account many intricacies. However, these added details only made the case more compelling. Just like the case of the mousetrap mentioned at the start of this article, all of the components of vesicular transport have to be present at once in order to function at all.

The molecular complexity of life has all the hallmarks of a Master Designer. We look forward to the time when God will destroy “the face of the covering cast over all people, and the vail that is spread over all nations” that presently prevents their acknowledgement of their Creator Isa 25:7).

References

  1. Alberts, B; Johnson, A; Lewis, J.; Raff, M.; Roberts, K.; Walter, P. “Molecular Biology of the Cell” (1994) 4th Ed. Taylor & Francis:  New York, NY, USA.
  2. Behe, M.J. “Darwin’s Black Box – The Biochemical Challenge to Evolution” (2006) 10th Ed. Simon & Schuster: New  York, NY, USA.
  3. Cooper, G.M. “The Cell – A Molecular Approach” (2000) 2nd Ed. ASM Press: Washington DC, MA, USA.

Diagrams

Anatomy of the cell: http://www.animalport.com/  img/Animal-Cell.jpg Last accessed 15th Sept. 2008  Gated transport: Nelson, D.L. & Cox, M.M.  “Lehringer Principles of Biochemistry” (2000) 3rd  Ed. Freeman

[1] Effectively there are three main transport mechanisms. Transmembrane transport

and gated transport both rely upon a portal in the membrane that selectively allows

proteins through. Transmembrane transport tends to involve a smaller channel in

the cell membrane and has no gate. We will ignore these complexities for the sake

of simplicity as both modes of transport are dependent on a transmembrane pore –

whether this is gated or not.