Proteins are organic compounds. If you remember, organic compounds are compounds that contain the element carbon. Common organic compounds include proteins, lipids, nucleic acids, and carbohydrates.
Proteins are made up of something called amino acids; amino acids are the building blocks of proteins. There are many different types of proteins, so they have many different roles.
EXAMPLEProteins are used in your body like enzymes, which allow you to break down food and build all the molecules of your body. They're also used for structure, transport, movement, regulation of cell activity and defense in your lymphatic system. Additionally, they're used as your hormones; they can even be used as receptors to bind hormones to target cells.
So proteins have many, many different roles and are thus a very important molecule in your body.
Amino acids are the building blocks of proteins and combine to form proteins.
The diagram below shows the structure of an amino acid.
|Amino group||—||C||—||Carboxyl group|
In the center, you have a carbon molecule that's going to be covalently bonded to a hydrogen atom, an amino group, a carboxyl group, and an R group.
The R group is going to be unique to each of the different 20 amino acids that there are. In each of those 20 amino acids, the rest of the structure will be the same, but the R group will be different. One amino acid is going to have a different R group than another type of amino acid. Each amino acid has its own R group.
Amino acids will make up proteins. The order of amino acids and the number of amino acids will compose different types of proteins. So there are many, many different types of proteins, depending on the structure of amino acids.
The structure of a protein has four different levels. As you go through the four levels, refer to the diagram below.
The primary structure of a protein includes a linear chain of amino acids. Remember, there are 20 different types of amino acids in total.
Suppose you have a chain of four amino acids. When you have amino acids together in a chain, you call that a polypeptide chain; the prefix poly means many. These amino acids are linked together in a chain, and each link in the chain is held together by something called a peptide bond.
The reason every amino acid has an amino group and a carboxyl group is that the amino group of the first amino acid will bond to the carboxyl group of the second amino acid to form a peptide bond, and so on. When you have many amino acids held together by peptide bonds, this is referred to as a polypeptide chain. Therefore, the primary structure of a protein is a polypeptide chain.
The secondary structure of a protein is a polypeptide chain that is twisted or folded. When the primary structure twists and folds, it produces the secondary structure of a protein.
The tertiary structure of a protein is made when that secondary structure starts to twist and fold even more, producing the overall 3D shape of a single polypeptide chain.
Just as some buildings only have one room, some proteins only have one polypeptide chain, and only have primary, secondary and tertiary structure. But just as some buildings have multiple rooms, some proteins are composed of multiple polypeptide chains. These come together to form the protein's quaternary structure.
The quaternary structure is formed when you have two or more polypeptide chains that are held together. After the polypeptide chain has been twisted and folded, then twisted and folded more, it is going to combine with other chains. Those other chains are all going to be bonded together.
Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND