Smooth vs. Rough Endoplasmic Reticulum (Smooth ER vs. Rough ER): the smooth and rough endoplasmic reticulum is the two known types of the endoplasmic reticulum that is used for the development of a system that has interconnection and consist of channels that are membrane-bound in the cell cytoplasm.
ER is an organelle with an enclosed membrane that is found in eukaryotic cells only. This ER has the composition of a network membrane which is called cisternae. The rough appearance that it has is provided by the ribosomes, which are bound on its surface. Rough ER does the synthesis and also stores proteins.
On the other hand, Smooth ER helps in the storage of lipids and proteins. The key difference between rough and smooth ER is that smooth ER does not have ribosomes that are bound, whereas rough ER has ribosomes bound to it.
Table of Contents
What Is Smooth Endoplasmic Reticulum?
Smooth ER is a kind of endoplasmic reticulum where there are no surface-bound ribosomes is called Smooth ER. However, some smooth ERs have surfaces bound to ribosomes. This type of ERs is known as transitional ER.
Structure of Smooth ER
Generally, these smooth ER are connected to an envelope that is nuclear in nature. They also contain some tubules that are located near the periphery of the cell. These tubes have further branches resulting in the formation of a network. Some dilated areas can also be seen to be formed, which are called sacs. This particular ER tends to increase the surface area that has been devoted to the ER action.
Functions of Smooth ER
A lot of smooth ER consists of some specialized cells. The smooth lipids are formed by the synthesis of ER in these cells, like steroids and phospholipids and steroids. The synthesis of lipid cells can also be found in the sebaceous glands, ovaries, and testes. The transport vesicles that contain proteins and lipids can also be found near the smooth ER.
These vesicles show detachment from the ER, and they move into the apparatus of the Golgi. Apart from lipid synthesis, smooth ERs can also be seen to be involved in carbohydrates and steroid metabolism.
They detoxify drugs, alcohol, and some natural metabolism products. They are also involved in the regulation of calcium ions in muscle cells. However, the smooth ER also contains glucose-6-phosphate, which is needed for the conversion of glucose-6-phosphate into glucose by getting involved in the process of gluconeogenesis.
What is Rough Endoplasmic Reticulum?
On the other hand, the rough endoplasmic reticulum is those ERs that are found with ribosomes that are bound to the surface. This is the ER which does the synthesis of proteins.
Structure of Rough ER
The appearance of the rough ER is determined by the ribosomes which are bound to its surface. This process of binding ribosomes on the rough ER is defined as translocon. These ribosomes are not those which are bound permanently with the ER organelles. They release and constantly bind from the membrane. There is a large double-membrane sheet called the Golgi apparatus, which is formed by the ER. These proteins are shuttled between Golgi and ER apparatus via membrane-bounded vesicles.
Functions of Rough ER
The binding of the ribosomes of the ER takes place for the formation of a definite protein-nucleic acid complex inside the cytoplasm. During the initial stages of the mRNA transition, this complex is formed that belongs to a protein in the pathway that is secretory. The beginning of this translation occurs in a free ribosome. Here, the first 5-30 amino acids do the encoding of the signal peptide.
On the amino acid chain that is growing, this signal peptide is recognized by a signal recognition particle (SRP). After that, there is a pause in the ongoing translation, and the ribosome complex does the binding to the translocon inside the rough ER. This translation continues to occur, again and again, resulting in the formation of an amino acid chain. This nascent protein then enters the RER lumen. Inside this lumen, some more modifications take place some post-translational modifications.
The signal peptide is removed by the peptidase enzyme. After the removal of the signal peptide, some ribosomes that are bound are again released back to the cytoplasm. Some ribosomes are associated with the ER continuously, and these are called non-translating ribosomes. Other than the processing and synthesis of proteins, the rough ER is also involved in synthesizing the integral membrane proteins and the lysosomal enzymes. There is some N-linked glycosylation that is also initiated at the rough ER.
6 Key Differences Between Smooth ER and Rough ER
|Basis||Smooth ER||Rough ER|
|Ribosomes||In the case of Smooth ERs, the ribosomes are absent||In the case of Rough ERs, the ribosomes are present|
|Location||The location of the Smooth ER is basically near the cell membrane||The location of the Rough ER is mainly near the cytoplasm|
|Origin||The origin of Smooth ER occurs by the process of ribosome shedding||The origin of Rough ER occurs from the nuclear membranes|
|Composition||The main components of Smooth ER are tubules||The main component of Rough ER is cisternae|
|Function||The Major function of Smooth ER is lipids synthesis and storing of proteins and lipids||The major function of Rough ER is the synthesis and storage of proteins|
|Localization||The main form of Smooth ER is in lipid form cells like glycogen storing cells in the liver, adipocytes, interstitial cells of the testis, muscle cells, adrenal cortex cells, leukocytes, etc.||The main form of Rough ER is the protein-forming cells like the goblet cells, pancreatic acinar cells, Nissl’s granules of nerve cells, and antibody-producing plasma cells.|
Endoplasmic Reticulum is said to be a system that is interconnected and consists of channels bound to membranes in the cytoplasm. Both rough and smooth ER play some role in the storage and synthesis of macromolecules. The Smooth ER does the production of lipids. They also store proteins and lipids. Whereas, the Rough ER synthesizes and stores proteins. The key difference between rough and smooth ER is the absence and presence of ribosomes on their surfaces.