Issues in Biology


Complex Structures

What it takes to make a synthetic cell

The cell theory states that cells only come from cells. Modern synthetic biologists use our understanding of the building blocks of cells to create a synthetic cell. What does it take to synthesize a cell? Let's first look at the major parts that make up a cell. We will use only bacterial (or prokaryotic) cells as a template:

Genome (or chromosome)
Cell wall and cell membrane
Protein translation machinery (ribosomes, transfer RNAs)
Metabolic enzymes
Cytosolic mix of ions and metabolites

Now, these components are found in various amounts that differ over time. We have looked at self-assembly and this is indeed a strategy followed in laboratories. It means to put together components of a complex system relying on them to interact in predictable ways to generate a higher order structure and function. To make a synthetic cell is a claim of using synthetic components and adding them together in the right proportions that allows them to behave as a whole, in this case a cell.

The recent claim by Craig Venter of a synthetic cell falls short of such an approach, as it is actually the use of a synthetic chromosome in an already existing cell.

What would it take for someone to take credit for the first fully synthetic cell? I would suggest that the following has to be achieved. This list sets a very high standard, as it should, because the claim of recreating life in the test tube is indeed a very great claim:

Make a synthetic membrane with a cell wall around it.
Add the necessary synthetic DNA, tRNA, and ribosomes.
Add the necessary metabolic enzymes, metabolites and electrolytes.
Insert the necessary membrane transporters into the cell membrane.

If this 'cell' construct starts to metabolize, synthesize proteins and RNA, replicate the DNA followed by cell replication, then and only then have you created a simple, cellular form of synthetic life.

There are valid scientific and philosophical reasons to reject the claim that this cell shall be called a synthetic cell.



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