It All Starts With Proteins

Understanding the Code of Life (Part 1: Proteins)

We are going to start our discussion of DNA in a rather unexpected place – your home. What I want us to think about for a moment is what does it take for your home to 'function' as a home? Obviously, there are the day-to-day chores – cleaning and tidying up, taking out the garbage, cooking and preparing the food, etc. And then there are the occasional issues that arise – a burst pipe, backed-up toilet, broken door handle, etc.

Now, clearly someone has to perform these tasks and, more often than not, they need the right tools and/or parts to perform them. Someone has to sweep the floor and they have to sweep it with something. Similarly, someone has to fix that broken pipe and they are going to need a variety of tools and parts in order to do so.

In short, a home simply can't function as a home without various people performing various tasks with the appropriate tools and parts needed for those tasks.

So it is with biological organisms – from simple cells to human beings and all creatures in-between. In order to live and function our bodies need to perform various functions. Oxygen needs to circulate through our bodies, hair needs to grow, etc. These functions don't just happen by themselves (just like your room doesn't get clean by itself, no matter how much you wish it did).

The question is how does it happen? And the answer is proteins.

Proteins Get the Job Done

Proteins are the workers of the body. They are the biological molecules that actually get things done. They move our muscles, fight foreign 'invaders' (such as bacteria and viruses), build our bones, and more. See for yourself:

But proteins are more than just workers – they are workers and tools all-in-one. What's more, proteins are specialized workers with specialized tools, with different proteins 'assigned' to do different jobs.

Now, here's the kicker. What determines the function (or should we say job) of a particular protein is its particulate shape. Each protein has a unique shape which enables it to perform its particular job, as the following video demonstrates:

Returning to our analogy of a home, we can get a better idea of what this all means. You would not try to cut wood with a spoon and I hope you would not try to eat your cereal with a saw.

Hemoglobin and an Antibody data-verified=
Hemoglobin (top) and an antibody (bottom). Their unique shapes enable them to perform their unique functions.

Using the right tool for the right job is crucial to completing the task as required, and part of what makes a tool right for the job is its shape. A saw has a unique shape, as does a spoon; each tool being carefully molded to the task assigned to them.

And so it is with proteins. The shape of each protein enables it to perform the task at hand.

Of course, this leads us to ask an obvious question. How does a particular protein get the particular shape it needs to perform its particular job? And the answer to that question involves yet another molecule called an amino acid.

The Building Blocks of Proteins

Just like letters are the fundamental units of words and bricks are (or at least can be) the fundamental units of houses, so too amino acids are the fundamental unit of Proteins.

That is to say, if you want to create a protein you need amino acids. And not just any old amino acids will do. Rather, you need the right amino acids placed in the right order (just like you need the right letters placed in the right order to form words and sentences).

Molecular Structure of Amino Acid
Molecular Structure of Amino Acid

So theoretically speaking making proteins should be simple; just string together the right number of amino acids in the right order. Well, as the saying goes – easier said than done.

The problem is that there are 20 different types of amino acids and proteins often times consist of chains of hundreds (if not thousands) of amino acids. What's more, there seems to be little room for error. Use the wrong amino acids in the wrong place and the protein will most likely fail to function at all or at least won't function properly (sometimes with serious repercussions for the organism in question).

So, to make a protein you need to get the string of amino acids just right. And that's not such a simple thing to do. To understand why, consider a simple analogy.

Imagine a safe with 100 dials, each dial numbered 1 – 20. Now, let's imagine that there are a few hundred combinations that will open the safe. How easy is it via trial and error to come upon one of those combinations.

Some simple math will tell us that it is not easy at all. There are 20 100 different possible combinations for this safe. That's a four followed by one hundred zeroes. Clearly the odds of landing upon a successful combination is extremely low (to say the least). You could quite literally spend every waking second of your life searching for a a working combination and never find it. The odds are just too heavily stacked against you.

This is basically what is involved in selecting the right sequence of amino acids to form a protein. There are twenty different amino acids and proteins often times consist of hundreds (and sometimes even thousands) of amino acids. Clearly there needs to be some sort of mechanism or system in place for selecting and ordering the right amino acids in the right sequence.

Indeed, such a system does exists. It even has a name we are all familiar with – DNA.

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