Smooth endoplasmic reticulum is not bounded by ribosomes and helps in the storage of lipids and proteins. The rough endoplasmic reticulum is bounded with ribosomes and helps in the storage of only proteins.
The endoplasmic reticulum is the essential component of the eukaryotic cells and abbreviated as ER. It builds almost 10% of the total volume of the cell. Although it is an important component of the cell but not every cell possesses endoplasmic reticulum. For example, red blood cells do not have endoplasmic reticulum. Cells that produce a large number of proteins and oils have a large amount of ER. The endoplasmic reticulum is of two types; smooth endoplasmic reticulum (SER) and rough endoplasmic reticulum (RER). Both types of endoplasmic reticulum have many common characteristics but also differ from each other.
The endoplasmic reticulum is membrane-bounded organelle and made up of cisternae and tubules which are network-like structures. It works for the chemicals needed by the cells for their inner and outer environments. It produces, sorts and transports these chemicals and stores some of these chemicals such as proteins and lipids. It has cavities which occupy a significant space in the cytosol with the internal space lumen. It has connected with the nuclear membrane as well as with the cytosol by forming a connecting bridge between them.
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Comparison Chart
| Basis for Comparison | Smooth Endoplasmic Reticulum | Rough Endoplasmic Reticulum |
| Definition | Endoplasmic reticulum with smooth surface and tubule and reticule structures is called smooth endoplasmic reticulum | The endoplasmic reticulum with the rough surface because of ribosomes and cisternae in structures is called rough endoplasmic reticulum. |
| Location | Near the cell membrane | Near the cytoplasm |
| Originates from | From rough endoplasmic reticulum | From nuclear membrane |
| Ribosomes | They lack ribosomes | Have ribosomes |
| Composed of | Tubules and vesicles | Cisternae and a few tubules |
| Another name | Agranular endoplasmic reticulum | Granular endoplasmic reticulum |
| Function | Produce lipids and proteins | Produce proteins |
What is Smooth Endoplasmic Reticulum?
The smooth endoplasmic reticulum is also known as the agranular endoplasmic reticulum. As the name is depicting, it possesses a smooth surface which can be viewed under the microscope. It does not contain ribosomes so its surface appears smooth. It is dispersed throughout the whole cytoplasm of the cell. The smooth endoplasmic reticulum is attached with the nuclear membrane internally and also contains tubules that are located near the peripheral surface of the cells. Tubules from a branched network which is reticular in appearance. It also has dilated sacs like areas. Smooth endoplasmic reticulum increases the surface area of the ER to help preform the function. The smooth endoplasmic reticulum is formed from the rough endoplasmic reticulum when ribosomes are detached from RER. It does not help the synthesis of proteins but helps in the transportation of formed proteins.
Function
The main function of the smooth endoplasmic reticulum is the production, secretion, transportation, and storage of the lipids and steroids hormones along with the metabolism of the carbohydrates. It also helps in the manufacturing of the new membranes. In mammalian cells, smooth endoplasmic reticulum plays a significant role in detoxification of some drugs, alcohol and some other metabolic waste material. In liver cells, it provides the enzyme glucose-6-phosphate which actively helps in the metabolism (gluconeogenesis). SER also helps in the regulation of calcium ions concentration in the muscle cells. SER also helps in the synthesis of lipids. Lipids synthesizing cells are found in testes, sebaceous glands, and ovaries. Transport vesicles containing lipids and proteins are found near the smooth endoplasmic reticulum. These vesicles detach from the endoplasmic reticulum and move to the Golgi apparatus.
What is Rough Endoplasmic Reticulum?
The rough endoplasmic reticulum is also called the granular endoplasmic reticulum. It appears as the uneven surface under the microscope because of the presence of 80S ribosomes. The site through which ribosomes are attached to the endoplasmic reticulum is known as translocon. Ribosomes are not permanently bound components with the endoplasmic reticulum. Ribosomes constantly bind and release from the membrane. These are attached with RER through ribophorins. Rough endoplasmic reticulum has narrow pores under the ribosomes through which the biochemical are transported into the channels. RER is composed of cisternae which are flattened disk-like structures.
Function
The main role of the RER is the synthesis and transportation of the proteins to the other parts of the cells. It also does the modification of proteins. It synthesizes and transport antibodies, insulin, mucin, collagen, blood clotting factors, enzymes, and other important proteinaceous substances in cells such as fibroblasts, goblet cells, hepatic cells, B lymphocytes, and pancreatic cells.
Key Differences between Smooth and Rough Endoplasmic Reticulum
- Smooth endoplasmic reticulum does not possess ribosomes whereas rough endoplasmic reticulum has ribosomes on the surface.
- The smooth endoplasmic reticulum is formed from rough endoplasmic reticulum when they shed off ribosomes whereas rough endoplasmic reticulum formed from the nuclear membrane or envelop.
- The smooth endoplasmic reticulum is formed of tubules and vesicles whereas rough endoplasmic reticulum is formed of cisternae and a few tubules.
- The smooth endoplasmic reticulum is present peripherally attached to the plasmalemma whereas rough endoplasmic reticulum is present internally attached to the nuclear membrane.
- Smooth endoplasmic reticulum produces steroids, lipids, and glycogen whereas rough endoplasmic reticulum produces enzymes and proteins.
- Smooth endoplasmic reticulum lacks pores so the chemicals formed do not pass into the channels whereas rough endoplasmic reticulum has pores below the ribosomes so the chemicals formed transfer into the channels.
- Smooth endoplasmic reticulum helps in the formation of sphareosomes whereas rough endoplasmic reticulum helps in the formation of lysosomes.
- Smooth endoplasmic reticulum lacks ribophorins whereas rough endoplasmic reticulum has ribophorins that help in the attachment of ribosomes.
- Smooth endoplasmic reticulum provides vesicles for the Golgi apparatus whereas rough endoplasmic reticulum provides biochemical for the Golgi apparatus.
Key Similarities
- Both smooth and rough endoplasmic reticulum helps in the synthesis and storage of proteins.
Conclusion
In conclusion, smooth and rough endoplasmic reticulum has many differences but the main difference is the absence and presence of ribosomes respectively which gives a rough appearance to the rough endoplasmic reticulum. Both play a vital role in the production of biochemicals in the cells.