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Proteins: Structure, Function & Types

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Without proteins you couldn't survive. But how much do you know about them? This lesson will explore the structure and function of proteins, and list some types of proteins you might encounter.

Proteins: Function and Types

Meet Pete the Protein. When you hear the word 'protein', the first you may think about is a bodybuilder or a fancy protein shake, but there's so much more to Pete than bodybuilding and shakes. For starters, proteins, like Pete, can be found in all of your cells, where they help your body accomplish many tasks. It's safe to say, you couldn't even survive without Pete.

Pete and his fellow proteins can be found in enzymes, which help chemical reactions occur faster in your body. For example, the enzyme lactase allowed you to digest the sugar in your mother's breast milk when you were a baby! Pete can also be found in collagen, keratin and elastin, all of which are structural proteins that make up ligaments, tendons and hair.

The next time you fight off a cold, you can thank Pete; that's because antibodies, or molecules that help protect your body from invaders, like viruses and bacteria, are made up of proteins. In addition, your muscles are made up of proteins, as are many hormones in your body, including insulin. So, what makes Pete a protein?

Protein Structure

Proteins are made up of amino acids, or organic compounds, that are linked together through peptide bonds. There are 21 amino acids found in humans. Different combinations of these amino acids make up all of the proteins you can think of, from the fibrin that forms scabs on a cut finger to a protein that allows rattle snakes to detect body heat.

Although amino acids differ from one another, they share some characteristics such as:

  • An amino group
  • A carboxyl group
  • A unique side chain that is often depicted as 'R'

A carboxyl group is a carbon that is double bonded to oxygen and also bonded to an oxygen and hydrogen atom. An amino group is a nitrogen atom bonded to two hydrogen atoms. Take a moment to review the structure of an amino acid before we go on.

The Structure of an Amino Acid
amino acid

Each amino acid is determined by its unique R-group. In the diagram below, instead of using an 'R', the molecules are written out. See if you can find the groups that make the amino acid an amino acid.

Carboxyl and Amino Groups
amino acid

The unique R-group gives the amino acids their unique characteristics. For example, some are soluble in water, whereas others are not. Some are neutral, while others have a positive or a negative charge.

Remember how we said a protein is formed when amino acids are joined together in a peptide bond? Peptide bonds form when the carboxyl group of one molecule combines with the amino group of another molecule to release a water molecule. Groups of amino acids bonded together are known as polypeptides, and all proteins are polypeptides - just like Pete. When amino acids link together through peptide bonds to form polypeptides, polymerization has taken place.

Formation of Peptide Bonds
peptide bond

Primary, Secondary, Tertiary and Quaternary Structure

Now that we know what Pete looks like and how he works, let's look at his structure. Think of primary, secondary, tertiary and quaternary structures as different ways to look at proteins. For example, think of the primary structure as the 1-dimensional blueprint and the quaternary as the actual structure.

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