English: Mucin is a glycoprotein constituent of mucus. This is a drawing of Mucin and how it looks at the molecular level. Number 1 is the Cytoplasmic Region, Number 2 is the Transmembrane Region, Number 3 is the Core Protein and Number 4 shows O-Linked Glycans.

Mucin is a glycoprotein constituent of mucus. They coat the cells lining the respiratory, digestive, and urogenital tracts and sometime even skin. Their function is to protect the epithelial cells from infection, dehydration, physical or chemical injury, as well as an aid in passage of materials though a tract. The functions of mucins are dependent on the ability to form viscous solutions or gels. Mucin are structures that are long and extended and are not as flexible as you would imagine. The diagram is depicting what mucin looks like at the molecular level and the diagram is depicting, the number one is pointing to the Cytoplasmic Region, the number two is pointing to the Transmembrane Region, the number three is pointing to the Core Protein and the number four is pointing to the O-Linked Glycans.