No, myoglobin is not a quaternary structure. It is classified as a tertiary structure. Myoglobin is a protein that consists of a single polypeptide chain and is primarily found in muscle tissues, where it plays a crucial role in oxygen storage and transport.
The structure of myoglobin includes a heme group, which is responsible for binding oxygen. While it does have multiple regions and interactions that contribute to its overall shape, it lacks the multiple subunit composition characteristic of quaternary structures, which involve the assembly of more than one polypeptide chain. In contrast, proteins like hemoglobin do exhibit quaternary structure, as they are made up of four polypeptide chains working together to transport oxygen efficiently in the bloodstream.