How Mad Cow Disease Works

Once in a while, there will be reports of mad cow disease, scientifically known as Creutzfeldt–Jakob disease in humans. But unlike most deadly diseases, this isn't caused by a virus, a bacteria, or chemicals leading to cancer. It's caused by prions.

How do prions work?

Well the first question we need to explore what proteins are, and how they work. Proteins are microscopic structures in your body's cells that do all kinds of things simply by their shape alone. Sometimes proteins can be structural proteins, which would be like the bricks holding up your house or the legs holding up your chair. Without it, your cells would collapse. Sometimes proteins can be enzymes, which automatically change different proteins without wearing itself out. It's like a hammer that no one needs to control, or one of those automatic vacuum cleaners. Other proteins are transport proteins, which are the doors to your cells. Unlike your house's doors, however, they don't let everything in. Most proteins only let certain molecules inside, and thank goodness they do, because otherwise your cell would be a mess. Finally, there are receptor proteins and signaling proteins, where the signaling protein touches the receptor protein and makes things happen in the cell, just like when your finger hits the button on the remote control, and the TV turns on. 

So let's review here:

Protein	Description and Function	Household Analogy	Examples
Structural	Proteins that shape the entire cell	The bricks holding up your roof	Actin in your muscle cells
Enzymes	Proteins that change other molecules (called substrates)	Tools like hammers and wrenches that can build and take apart stuff	RNA polymerase, lysozyme
Transport	Proteins that only let certain molecules into the cell	Doors (that only let in certain people)	Glucose tranporters, GABA transporters
Receptor	Proteins that make the cell do something when triggered by the right protein or molecule	A keyhole, or a lightswitch	Neuroreceptors
Signaling	Proteins that tell the cell what to do	A key, or a hand flicking the lightswitch	Neurotransmitters

So as you can see, proteins do all kinds of stuff.

Proteins work by their structure. Just like a hammer can't do the same thing a wrench does because of its very shape, proteins that are shaped differently do different things. 

There are four levels of proteins. Each levels becomes more and more complex. The first level is called the primary structure, where a bunch of amino acids are strung together into a string. This combination is unique to a protein. 

The second level is when bits and pieces of the string attract each other. This creates a 2D shape, more or less. Instead of a string that goes in one line, it can form shapes similar to alphabet letters such as S and L. This is called the secondary structure.

The tertiary structure starts to create a 3D shape, because of more overlapping, attraction, and so forth. This is what really gives it its true shape, and so determines its function.

When you combine a bunch of pieces of separate tertiary structures, you get the quaternary structure. 

Prions are proteins that not only change other proteins, like an enzyme, but change that protein to look and act like itself. It does this by changing the secondary and tertiary structure of a protein that has the same primary structure. It's as if your hammer was able to touch a wrench, and turn your wrench into another hammer. And then you've got two hammers converting other tools into even more hammers! Freaky, huh?

Actually, prions are a lot like zombies. In the science fiction world, zombies infect other humans, turning normal human beings into zombies, who can then create more by infecting other human beings. And unfortunately, this disease does turn a normal person's brain into that of a zombie's.

When you take these normal proteins in your brain, and these prions change them into more prions, they tend to clump up. When they clump up in your brain cells, they stop functioning and die out, similar to when a pipe is stopped up it can actually leak and burst. This is what causes brain damage, and eventually, death.

Many people get this disease from cows, particular cows who are fed the remains of other cows. Frequently, in order to save money, many beef companies feed their cows the parts of cows that they can't sell as meat. This means the spinal cord and the brains. Of course, once you've got a prion in one cow's brains and you feed it to another cow, you're spreading the disease.

You can't kill the prion by cooking it, or even surgical sterilization procedures. It's nearly impossible to destroy.

This sounds like something out of a science fiction story, but it's not. Unfortunately, it's for real. And the kicker? It only costs a few more cents per pound to test every cow. But a few more cents per pounds translates into millions of dollars of extra profit for a single company, so they're willing to expose us to risk for just a bit more money.