Each living organism is composed of basic unit of life i.e., the cell. Though there are different cell types (oval, round, cylindrical) they have the same structural organization.

Each cell is lined by a protective outer covering called cell membrane, which holds the fluid called cytoplasm. Cell membrane is bilayer in nature and is made up of phospholipids. The bilayer makes it polar at one end and non polar at the other end. This facilitates selective absorption of particles in and out of the cell. The cytoplasm also called as cytosol, maintains and carries out all the vital functions of the cell by means of its organelles.     

Both the prokaryotes (primitive forms) and eukaryotes have cell organelles. But eukaryotes have well developed cell organelles. Cell organelles are sub cellular structures which do the compartmentalization and serves different functions. They not only serve several functions but also hold the cytoplasm intact.

Nucleus, Golgi bodies, Endoplasmic reticulum, Ribosomes, Lysosomes, Peroxisomes are examples of cell organelles.

Endoplasmic Recticulum- EssayCorp
Scanning electron microscopy image showing the structure of endoplasmic reticulum (ER), Golgi (G) and Mitochondria (M).

What Does The Endoplasmic Reticulum Do And Its Functions?

Most (50%) of the membrane surface is provided by the endoplasmic reticulum to the cell. It is found only in eukaryotes (plants and animal cells) and plays a major role in producing lipids and proteins. They are first observed by K.R.Porter.  

It is a complex and large structure in the cytoplasm and spans between the cell membrane and the nucleus. It’s large and dynamic structure assigns several critical roles like calcium storage, lipid (fats) and protein synthesis and their transport and also protein folding. Basically, each structure is composed of three elements. i.e., tubules, sheets and the nuclear envelope. 

The endoplasmic reticulum is composed of a group of interconnected sac-like structures called tubules. These tubules collectively modify and produce the proteins and lipids. It is bilayer in structure i.e., covered by a protective membrane. This membrane has its origin from the nucleus.

Basing on the function and presence of ribosomes, the endoplasmic reticulum is classified into two types, rough endoplasmic reticulum (Rough ER) and smooth endoplasmic reticulum (smooth ER). These are the parts of Biology.

Both these forms are present in both plants and animal cell types. Though there are two different types, they appear together and coordinate the cell activities.   

Basing on the presence and absence of ribosomes on their structure, they are divided into rough and smooth endoplasmic reticulum respectively. As such cell types which are involved in the protein synthesis are rich in rough endoplasmic reticulum and the cell types which are assigned to produce lipids are more in smooth endoplasmic reticulum.

What Does Rough Endoplasmic Reticulum (RER) Do In A Cell & It’s Definition?

They are made up of flattened convoluted sac-like structures sealed at both their ends. These structures form the connective structures between the nucleus and cell membrane. As such they do share their lipid bilayer structure. As mentioned earlier they are studded with ribosomes on their cytosolic face i.e., towards the open end. Rough endoplasmic reticulum is distributed all over the cell but mostly concentrated around the nucleus and Golgi bodies.

The Role Of Rough Endoplasmic Reticulum:

  • Ribosomes are called protein factories of the cell as they synthesize the proteins during the process of translation. As these ribosomes are studded on the RER, rough endoplasmic reticulum is the site of protein synthesis.   
  • The RER in coordination with ribosomes aids in translocating the polypeptide chains and amino acids into their lumen and sorts out the proteins. In other words, the polypeptides assembled in the cytoplasm will be sorted and labeled with a peptide signaling ensuring they are transported to the right place and does the right function. This peptide signal decides the fate of the protein.
  • The proteins produced are given an identity within the lumen of the rough endoplasmic reticulum. The proteins taken into the lumen will be modified and folded giving them the basic structural identity. As such the proteins become eligible for the lock and key principle.
  • They are also called the quality control department. Protein sorting out takes place in the lumen of rough endoplasmic reticulum. The proteins folded are absorbed or rejected basing on whether they are folded correctly or incorrectly. Once accepted they are translocated to the Golgi bodies for finishing.
Endoplasmic Recticulum- EssayCorp
The structure of Endoplasmic reticulum showing SER and RER.

What Is The Smooth Endoplasmic Reticulum Made Of & It’s Definition?

The absence of the ribosomes on the structures confers the name smooth to the endoplasmic reticulum. As such the cell types which are essentially involved in lipids production are rich in smooth endoplasmic reticulum. They are also made up of the same structure as of RER but the tubules are more tubular in nature with fewer convulsions. They are fairly distributed all over the cytosol.

The Role Of Smooth Endoplasmic Reticulum:

  • They are sites of production of lipids.
  • They sometimes help in the metabolism of lipids and their allied products.
  • It also aids in synthesizing steroid hormones in most of the endocrine glands (Adrenal glands).
  • Glycogen is stored in the form of vesicles on the surface of smooth endoplasmic reticulum. SER breaks down these glycogen molecules into glucose to release energy (especially in liver cells).
  • It also acts to reduce the toxification of several organic chemicals from the cytoplasm. SER brakes down such harmful organic chemical moieties into simpler water soluble components making them safe for the cell.
  • Liver cells which are usually called detoxifying organs are rich in this smooth endoplasmic reticulum. Alcoholic compounds which are either consumed directly or produced as end products from food need to be detoxified from the body. The liver takes the lead in doing so. In doing this function, the SER sometimes doubles its surface area to overcome the load of alcohol and other poisonous compounds.   
  • Muscle contraction takes place with the help of calcium ions. And such ions are released by the SER helping the muscles in contraction.

To conclude, ER is an important cell organelle which takes a majority of the work load next to nucleus. Protein synthesis and lipid synthesis and some other critical functions are carried by them. Some of the harmful drugs which are usual intake during diseases are also detoxified by the smooth endoplasmic reticulum.And also if you need efficient assignment help on Biology or any other subject, please contact EssayCorp.

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  1. ryan February 21, 2017