Tuesday, December 31, 2013

On mitochondria

In 6th grade, you labeled your cell diagram, not quite understanding what you were doing, but enjoying picking the colors from your box of crayons, coloring the pill-shaped organelle a Crayola cadet blue.

In 8th grade, you learned that the mitochondrion was where oxidation and the Krebs cycle took place (even though oxidation and Krebs were just sounds to memorize to please the teacher). You learned that this was the cell's power plant. You imagined a tiny engine burning gasoline.

In high school you memorized the Krebs cycle, took the Biology AP Exam, and managed to slip into a decent college. You slogged through biochemistry, and eventually became a physician.

But you really never got it then, did you?

Mitochondria reside in our cells--they are sort of us, but not really--they carry their own DNA, and they descend from other mitochondria carried by your mother. And her mother. And her mother's mother.

Coloring them was about as exciting as mitochondria ever got.


Three decades ago I sat in the auditorium of the American Museum of Natural History. The teacher had primed our class, so when the serious man on stage asked what energy was, I knew the right words to say.

I raised my hand.
I started to open my mouth--I knew the words, my teacher was already smiling.

I did not say them. I stared at my feet.
"The ability to do work" caught in my craw.
The words explained nothing to me, and still do not.

My teacher's disappointment was once enough motivation for me to answer a stranger's question, even if I did not understand my own words.

At least until 6th grade.


Oxygen combines with fuel to release energy--light and heat. The oxygen does not contribute to the energy released--it "simply" accepts electrons, allowing bonds to break and reform.

If this happens fast, you get fire. Oxygen grabs electrons and protons, forming water. Hold your hand over a barbecue--the moisture on your palm is not just sweat. Hold a glass beaker over an open flame--water condenses on the cool glass. Try it.

Oxidation can happen slowly, too. The rusting rims of your child's bicycle left out over winter warms the frigid air as metallic iron morphs into ferric oxide. Rust releases heat. Molecules vibrate more quickly as electrons shift.

I know the words, but still do not trust them.

In 1978 I shoveled iron turnings on the docks, my feet warming up despite thick work boots. Until then I did not believe that rusting iron releases heat. Even more important, I had no reason to believe it--I no longer trusted teachers.

My favorite students are those who do not trust my words now--"show me!"
And I do.


The warmth and movement of your lover comes from the sun.
You twist together, heat and motion.
Mitochondria hum.

In the morning, the sun rises, as it has, as it will.

The apple I eat courses through my veins as sugar, sugar that feeds the mitochondria.

Heat, water, and carbon dioxide are released. I step outside into the New Year chill, and see my breath. The water vapor dissipates, to return as rain. The carbon dioxide eventually feeds the spring garden, a few molecules going back to the apple tree, where the sun's energy restores a bit of order.

Leslie and I make up our shared bed, laughing at the entropic knot of sheets and blankets.

Our body heat comes from our mitochondria, trillions of symbionts stoking our fires.

If the soul resides anywhere, it resides here in the mitochondria.
After our last agonal gasp, our corpse quickly cools. The change is startling, even to experienced hands.

I've pronounced a lot of dead people, feeling for a pulse, watching for chest movement. Either can fool you. The abrupt onset of cold, however, tells the story. The mitochondria have stopped working.

You are dead.

The best parts of science get buried in the details.

Nicotinamide adenine dinucleotide.
Adenosine triphosphate.
Alpha-ketoglutarate pathway.

My students yawn at the details.

I try to use a 3D model. Nitrogen atoms are, alas, painted blue.
"The red balls are oxygen, the blue balls...."

My frontal lobe edits too slowly today. I have their attention now--"Blue balls, he said blue balls!"--and the room now vibrates with a different kind of heat.

I breathe. I eat.
I use the energy released from the food I eat today to start preparing for the spring garden.

A garden is a lovely lie--a pretense of order in the midst of organic chaos.

I teach about the Krebs cycle in a classroom without windows.
I want to stop class, run outside, show my lambs the inexplicable dance outside, where a tiny portion of sunlight happens to hit our world, and carbon dioxide and water happen to get reorganized into food, that we happen to eat, to be.

Grace. Dharma. Science.

Hey, it's my blog, I'll repost if I want to!

1 comment:

Unknown said...

Re-post away...

Perhaps it was a good thing you never got out "The ability to do work" schtick in case you weren't ready to define "work".

Grounded more in the physical sciences as I am, I tend to fall back on Newton as a touchstone for things that move (or don't).