Question

Differentiate between rough and smooth endoplasmic reticulum. How is endoplasmic reticulum important for membrane biogenesis?

Answer 1

Differences between rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) are as follows:

RER	SER
RER has ribosomes attached to its surface.	SER does not have ribosomes attached to its surface.
RER takes part in protein synthesis.	SER takes part in the synthesis of lipids and fats.

Membrane biogenesis (i.e., formation of plasma membrane) is carried out by the joint activity of some cell organelles.
The proteins and lipids, essential for building the cell membrane, are respectively manufactured by rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). The lipid molecules for the cell membrane are formed and inserted into the membrane of smooth ER by smooth ER itself. The protein molecules of the cell membrane are mostly synthesised and inserted into the membrane at the level of rough ER. In the process of glycosylation, short chains of sugars, called oligosaccharides, are added to molecules of proteins and lipids at the level of Golgi apparatus. In this way, the formation of plasma membrane (membrane biogenesis ) involves the following organelles, all forming the so-called endomembrane system :
Rough ER → Smooth ER → Golgi apparatus → Secretory vesicle → Plasma membrane.