Monday, February 26, 2007

The Bio Economy

Derek Lowe has another post about the Biotech industry's glorious pool of red ink. A number of the comments are useful to think about -- perhaps most industries go through such a long boot phase, but we forget because we watch them when they are established (and often in decline).

Thinking about biotech losses reminded me of the parallels that are often drawn between the human world and the cellular world. The molecule adenosine triphosphate, or ATP, is often described as the currency of the cellular world. This is because it is the most common driver of reactions in the cell. There are other such molecules, such as ion gradients & ATP's cousin GTP, but ATP is far-and-away the most common currency -- the dollar of the molecular economy.

There is a key difference between human currency and molecular currency, one that I confess I never can quite convince myself I understand on the human side. While there are occasional money changing operations in the cell, such as using ATP to regenerate the other nucleotide triphosphates, when ATP is used to drive a reaction the energy the currency is consumed. While sometimes that energy sets up another process, many times the chain of payment ends there. When a kinase phosphorylates a protein, there is no regain of that ATP when the phosphate is kicked off by a phosphatase. When nucleotide triphosphates are used to build DNA or RNA, that energy is used forever.

But in the human world, our dollar bills don't crumble each time we use them. I bought a pizza tonight, the pizza shop will in turn pay its suppliers and employees, who will spend the money again and again and again. Nowadays the bulk of my transactions are purely electronic (such as the pizza purchase), so there is no money to crumble. It's never been obvious to me the economic equivalents of entropy; the economy seems too close to a perpetual motion machine to be believed.

There are a few other parallels though. For example, glycolysis initially requires an investment of ATP to yield far more ATP; you need money to make money! Some molecules use clever barter strategies to avoid needing to deal with currency -- for example, DNA topoisomerases perform bond swapping maneuvers so that they can rejoin the DNA they have broken without requiring any further ATP. Money makes the world go 'round; ATP makes bacterial flagella go 'round.

Gotta go -- as they say, time is ATP!

3 comments:

Greg said...

Hi Keith, the Jedi mind trick that economists play on us and themselves is that that money != energy. It must otherwise the economy, as you say, would be a perpetual motion machine, clearly not possible.

I suspect that money in fact equals oil and that the growth of the money supply is likely to parallel the increased usage of crude oil in the 20th century.

bioephemera said...

I've always hated the energy currency analogy, too. That, and "the mitochondrion is the powerhouse of the cell." What gobbledygook! It annoys me every time I have to say it to a class. But. . . it works pedagogically.

Derek Lowe said...

I think that the idea behind an expanding economy/stock market, etc. is that human capital is the driver (new inventions, markets, etc.) Otherwise, you'd figure that in a zero-sum world, everyone's standard of living would inexorably go down as time went on and population increased.