Proteins

Proteins are one of many types of natural polymers, and they are the most versatile by far. You name it, proteins do it.

What can proteins do? What can't they do!

Enzymes are proteins that make sure that chemical reactions in your body take place up to a million times faster than they would without enzymes.
Antibodies are proteins that help your immune system to fight disease.
When you get a boo boo, the bleeding stops because of blood clots, thanks to the proteins fibrinogen and thrombin.
Transport! Some proteins carry stuff from one place to another, or form tunnels (pores) in cell membranes that will let only specific molecules (or ions) through. Hemoglobin, a protein in your blood, carries oxygen from your lungs to your cells.
Strength and support! Other proteins like collagen and keratin are strong and tough and make up your skin, hair, and fingernails. Collagen also supports your cells and organs so they don't slosh around.
Motion! The proteins myosin and actin make up much of your muscle tissue. They work together so your muscles can move you around. Some bacteria have cilia and flagella made out of proteins. The bacteria can whip these around to move from place to place.

Yes! You are made out of protein! The image below is what the polymer (keratin) your hair is made of. This is that famous "coil of coils" structure which gives your hair the ability to bend and flex but still be strong enough not to break or pull apart when you comb it.

So, what are proteins?
Proteins are polymers made out of amino acids. They're naturally occurring, meaning they're made by animals, plants, bugs, fungi, and other living things - and that includes you!

A protein is actually a polyamide (a what?), but more about that later.

So, proteins are polymers of amino acids. What's an amino acid? (Glad you asked!!)

Amino acids have an amino end and an acid end. In the middle is a C (carbon) with an H (hydrogen) and a side group shown here as an R. (Think of R as the Rest of the molecule.)

That R group can be as little as an H or kinda big. There are twenty common amino acids in your body. Want to see 'em? Click here. Each one has a different R group.

For each protein that's made, the order of the R groups is VERY important because it determines the shape of the protein and the job it will do. To get the right order, cells use RNA that's copied from your DNA. The whole story is pretty complicated, and involves special enzymes and even different kinds of RNA. We won't go into it now - just trust that there's a whole system in place to make sure the right amino acids get put together in the right order.

So, how does your body make a protein?

1
First, hold 2 amino acids next to each other like this:
2
Take out the -OH and -H circled in red, and form a new bond. The -OH and the -H together make a molecule of water - H₂O.

3
Bring in the next amino acid!
4
Again, remove H₂O and form a new bond.
5 and up!
Keep adding amino acids and taking out water until the protein is done!

Want to know something else? Proteins also make up silk. Silk is such nifty stuff that scientists tried to make synthetic silk. They tried to make synthetic polyamides, and what do you know, they did it! The artificial polyamides are called nylons.

O.k., earlier we said that a protein is a naturally occurring polyamide, and that we'd get to that later. Hey, guess what?! It's later!

A polyamide is a polymer (of course!) that has amide groups in the backbone chain.
Here are two ways of looking at an amide group:

Remember what our little baby protein looked like? Every time we added an amino acid, we made an amide group! See the amide groups in blue?

Now, we said that a protein is a polyamide. Any old polyamide would look like this, and the R groups don't have to look like the middle of an amino acid. It could just be a chain of six -CH₂- units, or it could get more complicated.

Two Examples of Polyamides

Notice something weird about those two examples? They're both general examples of polyamides, but their repeat units would be different (so they'd have to be made using different methods and different monomers, even if the R groups were the same.) Want to learn more about polyamides and nylons? Click here!

You want more natural polymers? Then check out these:

Cellulose

Starch

Natural Rubber (That's polyisoprene to all you smarties out there!)

Natural Polymers

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