Saturday, June 8, 2013

molecular time vs. organic time

Yesterday I watched two short lectures on mechanical and electrical forces in the cell. The first focused on how bacteria or muscle cells move by constantly building filaments, i.e. hair-like strings of proteins, that push against the membrane.

The second lecture mainly discussed how electrical action potentials in neurons are created via cascading opening and closing of ion channels in the cell membrane.

In order for a bacterium to visibly move, it probably has to stick millions of protein molecules onto its filaments. In order for me to blink my eyelid, thousands of muscle cells have to do the same. In order for a signal to be propagated from one end of a neuron to the other, millions of ion channels have to open and close and transport ions across the membrane, which creates an electrical imbalance. For me to realize that I just bumped my head against the wall requires thousands (millions?) of neurons to fire.

So, for changes in my body that happen (literally) in a blink of an eye, millions and millions of molecular "machines" have to do their thing. As a relative newbie, I was flabbergasted not only by how much machinery is at work inside a cell, but even more by how FAST these processes are. The speed just blew my mind.

Then I started thinking: in order for me to think, neurons must fire. Perception requires detection of physical stimuli, translation of these stimuli into chemical signals, and again firing of many neurons. The smallest perceivable time unit is probably measured in hundreds of milliseconds - anything happening in shorter time intervals is perceived as "instantaneous". This is so simply because our cells require a certain amount of time to propagate signals, and many cells are involved in even the simplest perceptions.

Molecular machines are thus not particularly fast, but the *seem* fast to our brains, because our brains are necessarily slower by an order of magnitude. We perceive at "organic time", while molecular machines operate at "molecular time". Interpreting molecular processes in "organic time" makes as little sense as interpreting our life span in geological time or vice versa.  

So, my initial wonder about molecular speed is nothing but a newbie mistake - trying to make sense of what the biologists are talking about in the framework that makes sense to me - I was anthropomorphising molecules, as it were. From now on, I'll try to understand molecular processes as happening in molecular time.