Ask a biologist what the basic building block of life is, and she will tell you it’s a cell. Ask a chemist this question and she will tell you it’s an atom. Ask a physicist and she will tell you that it’s something even smaller, some miniscule particle with a weird name.
For the purposes of this story we’ll adopt the biologist’s definition: a cell.
If you search for a Google image of a cell, this guy pops up:
Not exactly what I had envisioned. Let’s go with this one:
If you’re human (a quick check in the mirror should clear that up) your body has more than one trillion cells. One trillion! This is 10 to the 12th power, or 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10 times 10, or 1,000,000,000,000.
I’m thankful someone else figured this out, because I’m not the type to sit still long enough to count that many cells. Here’s how it would play out:
Curious child: “How many cells are inside my body?”
Sarah: “Hmmm, I will count them. Let’s start with your skin cells. Stick your hand under the microscope and I’ll start counting. One, two, three, four…”
[Five minutes later]
Sarah [visibly bored of this activity]: “Yeah, so, Google it is…”
Each of your trillion cells has a cell membrane. The membrane is a protective covering around the cell, to keep the good stuff in and the bad stuff out. Good stuff: DNA, nutrients, water. Bad stuff: foreigners (a virus, a toxin).
Science teachers often use an egg analogy for cell biology. Hard-boil an egg and you have a pretty good model of a cell. The eggshell is the cell membrane. The white part is the inside of the cell. The yellow yolk is the nucleus.
The cell membrane (the eggshell) has several gates to let stuff in and out. It’s vital that your cell has exactly what it needs; nothing less and nothing more. The gates help ensure this.
With the egg analogy it’s hard to simulate the gates, so just imagine them. The gates are called channels, and the cell membrane has different channels, one for each type of stuff. There’s a channel for water, a channel for sodium, a channel for potassium, a channel for calcium, and so on.
You might be wondering what a channel is or what it looks like. A channel is a big protein and it looks like a bunch of ribbons. Below is a close-up of the potassium channel:
The “intracellular” portion is what’s inside the cell (the white part of the egg). The “membrane” portion is lodged in the cell membrane (the eggshell). The “extracellular” piece hangs out of the cell (outside the eggshell).
That potassium channel regulates how much potassium goes in and out of the cell. If the cell has too much potassium, the channel opens and flushes the potassium out. If the cell has just the right amount of potassium the channel closes and stays closed.
If the cell changes its mind, it re-opens and thieves the potassium back.
These channels constitute a vast communication network among the cells in your body. Cells release potassium to talk to other cells. Seriously. It’s not like they have [insert your favorite type of social media here].
The talking is in the form of electrical signals. One cell’s potassium channel opens and the cell releases potassium. A nearby cell’s potassium channel opens and the cell takes the potassium in. Thanks, potassium channels! You just transmitted an electrical signal!
Since the channels control the communication between cells, if you mess with a channel you have a major problem: cells can no longer talk to each other. The solution is simple: leave the channels alone.
Easier said than done. Channels are the major targets of toxins.