In this article we will discuss about the interrelationship of the different cell membrane.
It is generally believed that a close structural and functional relationship exists between the different membrane systems of the cell (Fig. 3-15). Some authors have proposed a terminology for the different membranes viz.
Novikoff has suggested GERL indicating close functional relationship between Golgi Complex (G), ER and Lysosomes (L).
It was Watson who demonstrated continuity between the ER and the outer nuclear membranes. In fact, space between the two nuclear membranes has been shown to open into the channel enclosed by the ER membrane.
Some authors believe that ER is, in fact, extension of the nuclear membrane. However, the former only possesses ribosomes on both of its surfaces while ribsosomes are only present on the outer surface of nuclear membrane.
Biochemical studies have shown differences in the two types of membranes in regard to enzymatic activity, protein and lipid contents.
There is also some thinking that outer nuclear membrane is an undifferentiated component of ER. Sometimes ER is shown to be in conjunction with the plasma membrane. This may be a sort of communication with the outer cell environment.
In the following a summary on the origin of the different cell membranes is given:
(i) Golgi membranes have been shown to originate from ER, annulate lamellae, nuclear envelope or even plasmalemma.
(ii) Vesicles pinching off from GB fuse to constitute the plasmalemma.
(iii) Golgi complex cisternae give rise to primary lysosomes by blebbing. Lysosomes may also arise from ER.
(iv) Outer membrane of the nuclear envelope forms vesicles by blebbing. These vesicles fuse to form annulate lamellae. Gradually these lamellae lose their pore complexes, gain ribosomes and develop into lamellae of ER.
