H5 Protein glycosylation

Many proteins synthesized by the ribosomes of the RER contain short chains of carbohydrates (oligosaccharides) and are called glycoproteins. The oligosaccharides are of two main types O-linked (to the OH side chain of Ser or Thr) and N-linked (to the NH2 side chain of Asn). Some proteins are attached to the plasma membrane by a third type of carbohydrate structure called a glycosyl phosphatidylinositol (GPI) anchor. 

O-linked oligosaccharides are synthesized by the sequential addition of monosaccharides to the protein as it passes through the Golgi complex. 

Translation in prokaryotes (H2) Translation in eukaryotes (H3) Protein targeting (H4) 

Three types Most proteins made by ribosomes on the rough endoplasmic reticulum (RER) 

In addition, several proteins are now known to be attached to the plasma membrane via a specific structure that involves carbohydrate, namely a glycosyl phosphatidylinositol (GPI) anchor. This is covered in Topic E2. 

---