What Are The Main Features Of Proteins?

Proteins are complex molecules that have many functions in animal and plant cells. There are two main types of protein ~ fibrous proteins such as the proteins that make up hair and nails ~ and globular proteins such as enzymes, antibodies and hormones.

All proteins are made up from small subunits called amino acids. These join together in long chains to form a long polymer molecule. The sequence of amino acids in a protein is known as its primary structure. The chain that is formed when many different amino acids link together is called a polypeptide and this coils up forming 3D structures such as an alpha helix. This folding is known as the secondary structure of a protein.

The helices formed then coil up around themselves forming another layer of 3D structure ~ the tertiary structure. Finally, some proteins combine with ions such as copper or iron ~ the final structure of the protein with everything in place is called the quaternary structure of the protein.