Question

In addition to their role in cellular secretion, the rough ER and the Golgi complex are also responsible for the biosynthesis of integral membrane proteins. More specifically, these organelles are the source of glycoproteins commonly found in the outer phospholipid monolayer of the plasma membrane.

Describe the synthesis and glycosylation of glycoproteins of the plasma membrane:

Integral membrane proteins are synthesized on the [golgi, rer, or ser], with [fatty acid or oligosaccharide] side chains added in part on the lumenal side of the [goldi, rer, or ser] (core glycosylation) and in part on the lumenal side of the [goldi, rer, or ser] (terminal glycosylation). Side chains therefore face the [interior or exterior] of both organelles as well as the [interior or exterior] of transport vesicles and become oriented toward the [interior or exterior] of the cell when the vesicles fuse with the plasma membrane.

Answer 1

Integral membrane proteins are synthesized on the rough endoplasmic reticulum (rer), with oligosaccharide side chains added in part on the lumenal side of the rough endoplasmic reticulum,rer (core glycosylation) and in part on the lumenal side of the Golgi complex (terminal glycosylation). Side chains therefore face the interior of both organelles as well as the interior of transport vesicles and become oriented toward the exterior of the cell when the vesicles fuse with the plasma membrane.