So let's begin by discussing a category of glycoproteins known as mucins. Now mucins, as we'll see in just a moment, are the major constituents, the major components of the mucus membranes that exist inside our body. So the mucous membranes can be found in the nasal cavity, in our air passageways, the bronchioles and so forth. Now mucints are basically these heavily glycosylated proteins that are produced and released by the epithelial tissue, the epithelial cells of our body. Now heavily glycosylated basically means there are many oligosaccharides, many sugar molecules found attached onto these proteins. The reason, the question is why?