Endoplasmic reticulum depending upon the presence or absence of the ribosomes :
1. Smooth endoplasmic reticulum (agrannular form). The outer surface of the membranes of such endoplasmic reticulum is smooth and does not bear ribosomes. The smooth endoplasmic reticulum is the major site for synthesis of lipid. In animal cells lipid-like steroidal hormones are synthesised in SER.
2. Rough endoplasmic reticulum (grannular from). bears ribosomes on its surface. Due to the presence of ribosomes the outer surface appears to be grannular or rough. Rough endoplasmic is continuos with the outer membrane of the nucleus. It is found in cells actively engaged in protein synthesis e.g. cells of pancreas, plasma cells, liver cells, goblet cells etc.
The endoplasmic reticulum is the network or of tiny tubular structures scattered in the cytoplasm. The endoplasmic reticulum is generally of two types smooth and rough endoplasmic reticulum. The rough endoplasmic reticulum has ribosomes attached to it whereas the smooth endoplasmic reticulum does not have ribosomes. The rough ER is generally found in cells actively involved in protein synthesis. Lipid synthesis is associated with the smooth endoplasmic reticulum.
Endoplasmic reticulum is of following two types:
A. Smooth endoplasmic reticulum - does not have ribosome.
B. Rough endoplasmic reticulum - has ribosomes attached to it.
A. Functions of smooth endoplasmic reticulum :
1. It is especially prominent in cells which are not involved in the synthesis of lipids.
2. It is involved in the synthesis of Golgi complex, lysosmoes and microbodies.
B. Functions of rough endoplasmic reticulum:
1. It is primarily involved in protein synthesis owing to the presence of ribosomes.
2. Packaging. The proteins manufactured in ribosomes are packed in RER. They are processed and packed in vesicles which are pinched off from RER.
3. Formation of glycoproteins. The carbohydrates and proteins are linked in RER to form glycoproteins.
4. Helps in the formation of nuclear envelops.
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