How is myoglobin's quaternary structure described?

Myoglobin is primarily known as a monomeric protein, which means it consists of a single polypeptide chain and does not have a quaternary structure. The role of myoglobin is to bind oxygen in muscle tissues, and its structure allows for efficient oxygen storage and release.

The quaternary structure refers to the arrangement and interaction of multiple polypeptide chains within a protein that has more than one chain. In contrast to myoglobin, hemoglobin, which is involved in oxygen transport in the blood, is a tetramer composed of two alpha and two beta subunits and does exhibit a quaternary structure.

Since myoglobin is a single polypeptide chain, it does not fit the descriptions of symmetric homodimer, tetrameric, or asymmetric trimer since those terms refer to proteins that consist of multiple chains. Therefore, the correct characterization of myoglobin's structure is that it is monomeric.