Re: Death before the Fall
Fri, 13 Aug 1999 13:34:44 EDT

In a message dated 8/3/99 6:46:48 PM Mountain Daylight Time, writes:

> Forgive my ignorance, but I don't understand the relationship between
> reproduction rates and metabolism. Perhaps more to the point, I don't
> fully understand what metabolism is.

There is nothing that needs forgiving; ignorance is only a problem when one
refuses to admit its existence, or uses it like a source of knowledge to
argue against known scientific fact.

The short answer to your question is that metabolism is general cellular
activity, which includes mitosis. As a general rule of thumb, the greater
the level of general cellular activity, the greater the rate at which
unicellular prokaryotes like bacteria reproduce. There is a maximal rate
determined by the genome (after all genomes can replicate only so fast), but
if the overall level of metabolic activity drops, replication, and thus
reproduction, slows down. At the same, it is during replication that most
bacterial transcription (make mRNA templates that are then used to make
proteins during translation) occurs, since the genome is already open.
Transcription does occur even when the genome is not replicating, but it
takes longer because the genome has to be opened to expose the genes. Since
metabolic activity is proportional to the level of transcription, the lower
the level of transcription the lower the metabolic activity. As such,
reducing the frequency of replication also reduces the overall level of
metabolic activity. As such, reducing the rate of bacterial reproduction to
the point where Adam and Eve would not burst within a day or two would also
reduce metabolic activity to the point where the bacteria would have trouble

Kevin L. O'Brien