ENDOPLASMIC RETICULUM
ENDOPLASMIC RETICULUM:-
It was discovered independently by "Porter(1945)and Thompson(1945). The name was given by "Porter"in 1953. Endoplasmic reticulum is a 3-dimensional,complicated and inter-connected system of membrane - lined channels that run through the cytoplasm. At places ,it is connected with plasmalemma as well as nuclear envelope. Plasmodesmata contain in the form of desmotubules .Endoplasmic reticulum divides the intracellular space into two compartments luminal and extraluminal.
Depending upon the nature of its membranes , endoplasmic reticulum is of two types e.g. smooth Endoplasmic reticulum and rough Endoplasmic reticulum.
SMOOTH ENDOPLASMIC RETICULUM:-
It has smooth membranes which donot bear ribosomes.It is ,therefore also called agranular Endoplasmic reticulum. This type of ER is found in cells engaged in the synthesis and storage of glycogen,fat and sterols. It is also commonly found in leucocytes .Smooth endoplasmic reticulum is mostly made of vessicles and tubules .sphaerosomes are believed to originate from SER.
ROUGH ENDOPLASMIC RETICULUM:-
It has rough membranes because a number of ribosomes occur attached to their outer surfaces. RER is,therefore,also called granular Endoplasmic reticulum. The membrane of the Endoplasmic reticulum bears a fine pore in the area of attached ribosomes to pass the synthesised polypeptide into the channel of Endoplasmic reticulum for transport. RER contain 2 types of glycoproteins e.g. ribophorin I and ribophorin II for attachment to ribosomes. On account of the presence of ribosomes,the rough ER is engaged in synthesising proteins and enzymes.
STRUCTURE OF ENDOPLASMIC RETICULUM:-
Endoplasmic reticulum consists of membrane lined channels or spaces .The channels or spaces contain a fulid called Endoplasmic matrix,which is quite different from cytoplasmic matrix present outside the reticulum. The membranes of Endoplasmic reticulum are 50-60 Armstrong thick. Endoplasmic reticulum can exist in three forms - Cisternae ,vessicles and tubules.
1)CISTERNAE-- They are flat interconnected sac-like parts of the Endoplasmic reticulum which are 40-50nm in diameter. The cistarnae are found in bundles where they lie parallel to one another.They occur in the cells actively involved in synthetic activity.
It was discovered independently by "Porter(1945)and Thompson(1945). The name was given by "Porter"in 1953. Endoplasmic reticulum is a 3-dimensional,complicated and inter-connected system of membrane - lined channels that run through the cytoplasm. At places ,it is connected with plasmalemma as well as nuclear envelope. Plasmodesmata contain in the form of desmotubules .Endoplasmic reticulum divides the intracellular space into two compartments luminal and extraluminal.
Depending upon the nature of its membranes , endoplasmic reticulum is of two types e.g. smooth Endoplasmic reticulum and rough Endoplasmic reticulum.
SMOOTH ENDOPLASMIC RETICULUM:-
It has smooth membranes which donot bear ribosomes.It is ,therefore also called agranular Endoplasmic reticulum. This type of ER is found in cells engaged in the synthesis and storage of glycogen,fat and sterols. It is also commonly found in leucocytes .Smooth endoplasmic reticulum is mostly made of vessicles and tubules .sphaerosomes are believed to originate from SER.
ROUGH ENDOPLASMIC RETICULUM:-
It has rough membranes because a number of ribosomes occur attached to their outer surfaces. RER is,therefore,also called granular Endoplasmic reticulum. The membrane of the Endoplasmic reticulum bears a fine pore in the area of attached ribosomes to pass the synthesised polypeptide into the channel of Endoplasmic reticulum for transport. RER contain 2 types of glycoproteins e.g. ribophorin I and ribophorin II for attachment to ribosomes. On account of the presence of ribosomes,the rough ER is engaged in synthesising proteins and enzymes.
STRUCTURE OF ENDOPLASMIC RETICULUM:-
Endoplasmic reticulum consists of membrane lined channels or spaces .The channels or spaces contain a fulid called Endoplasmic matrix,which is quite different from cytoplasmic matrix present outside the reticulum. The membranes of Endoplasmic reticulum are 50-60 Armstrong thick. Endoplasmic reticulum can exist in three forms - Cisternae ,vessicles and tubules.
1)CISTERNAE-- They are flat interconnected sac-like parts of the Endoplasmic reticulum which are 40-50nm in diameter. The cistarnae are found in bundles where they lie parallel to one another.They occur in the cells actively involved in synthetic activity.
2) VESICLES:- They are oval or rounded sacs of 25-500 nm in diameter. The vessicles appear as small vacuoles . They remain isolated in the cytoplasm. The vesicles are also called "microsomes".
3) TUBULES:- They are tube like extensions which may be connected with cistarnae or VESICLES to form a reticular system. The tubules can be regular or irregular ,branched or unbranched with a diameter of 50-100 nm.
Comments
Post a Comment