The Longest Word in the World (Chemical name of protein Titin) has 189,819 letters and will take you 3.5 hours to pronounce! In the video you can listen to a guy pronounce the whole word for 3hours 33minutes!
Methionylthreonylthreonylglutaminylarginyl…isoleucine. Technical; not in dictionary; disputed whether it is a word.
Titin also known as connectin, is a protein that in humans is encoded by the TTN gene. Titin is a giant protein that functions as a molecular spring which is responsible for the passive elasticity of muscle. It is composed of 244 individually folded protein domains connected by unstructured peptide sequences.These domains unfold when the protein is stretched and refold when the tension is removed.
Image credit: wikipedia