What’s inside us? Busy, busy towns.

7 Jun

The illustrators of biology textbooks have created countless diagrams to help students label and memorize our parts.  The pictures are useful and elegant, but they don’t tell us much about how our parts go.

Better for this than an anatomist’s best illustration of an animal cell is the cover of Richard Scarry’s “Busy, Busy Town.”

  In this drawing, a fox repairs a TV, a butcher weighs out a chop, a police dog guides traffic, planes and helicopters buzz overhead, and among a motley crowd of strolling pedestrians, Bananas Gorilla rounds a corner.

This is the world of the cell!

Each and every one of the cells that make up our bodies is a busy, busy town.  There are FedEx trucks, construction crews, traffic cops, taxis, shopkeepers and bureaucrats buzzing about, relating to one another and to the environment that we create for them when, for example, we eat, sleep, run, or nick ourselves shaving.  A cell has millions of inhabitants.  The vast majority are proteins that make up the cell’s structure.  A good number are workers and managers of everyday gadgets inside the cell.

Let’s say we eat a donut at an office party.  Down it drops into the belly, and while we are digesting, the sugar in the donut stimulates the pancreas to pump the hormone insulin into the blood stream, which touches all the cells in our body.  Sugar rush!

In most any given cell, in a person who is not diabetic, the insulin will enter the cell through a gate called the insulin receptor.  The insulin is a key, and the receptor is the lock that lives in the cell membrane.  The turning key starts the ignition of the cell that will take in donut-energy (calories and carbs) in order to grow, to store what’s not used, and to live another day.  How does this really work?  The receptor’s job is to phosphorylate a set of signaling partners, which basically means that, like a boss, it will call on its underlings to get to work.  One of its primary workers, IRS-1, is a protein that will do any of several things with the incoming insulin.  It will shut down a “death pathway” by telling the cell, “Food is coming, do not self-destruct!”  It will signal other molecules in the cell to turn on fat storage, to turn off the breakdown of fat since more is on the way, or to turn on protein production so that the cell can grow and divide.  In just one of many assembly lines of proteins in the cell that starts running on account of the donut, IRS1 activates Fyn, who taps GRB10, who taps MEK1/2, who taps Erk.   Erk is a signaling protein with an important job.  He is a bit like a contractor who helps keep the cell city growing.  He will gather other proteins and make the dangerous trek into the darkly lit cell nucleus, and there, in the market square he will recruit workers: plumbers, carpenters and electricians.  Each of these workers will go to the Home Depot of the cell to buy the single material she needs to do her job: piping, wood, or wires.  These materials are produced through transcription and translation—the Xeroxing of instructions contained in genes onto strands of RNA that are used to assemble actual amino acids that are used to build proteins.

The point here is that cells are mind-bogglingly vast and active.  And that donuts are kind of a big deal.

There is a kind of autonomy that our cells have in the context of our bodies.  They have jobs, they can collectively communicate, and they rely on and help to maintain a balanced choreography involving other cells and internal mechanisms. If the balance is off, the cell typically dies.  Our choices in life can impact this balance.

Just like the busy beavers inside of cells, we live in societies so large that we can’t even possibly follow all of the workings that make them operate.  We may have no idea what sanitation workers are up to, but we know that if they stop, we will notice because the garbage will start to smell, animals will come to rummage and disease will begin to spread.  The exact same thing goes on within each cell in the body.

News reporters can never know everything, but they can identify major players, spell out major issues, and sniff out trouble.  The goings-on within the busy towns of our cells are similarly so vast that we can only hope to glean their major workings.

To understand our bodies, we can start by seeing that the atom is similar to the molecule it lives in, the molecule is similar to the cell that it lives in, the cell is similar to the organ in lives in, the organ is similar to the body.  Bodies are like societies, which are like planets, which are like universes.

The big scientific question in the study of any of these things turns out to be: What are a thing’s nearest neighbors, and how do they relate to each other?

Cells are more than machines, and the hugest difference may be that, for example, cells can heal themselves.  No car can do that.  And our innards have an incredible ability to rearrange and assort themselves to, for lack of a good term, restore the balance of elements that are life-giving rather than life-taking.

To understand how to live well, to be happy, to reduce disease, to be good parents, it is helpful to see how our cells are a lot like us in our daily worlds.  They need us, and we need them.

 

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