As biologists probed deeper into the microcosm of cells, they found an entire autonomous biological system, with many organelles that served various functions. The trio consisting of Keith R. Porter, Ernest F. Fullam, and Albert Claude discovered the endoplasmic reticulum and published their research, in 1945. It was a very important discovery, as this cell organelle plays a major role in the functioning of every eukaryotic cell.
About Endoplasmic Reticulum
The first of the two words - 'endoplasmic' (endo = inside ) means that this organelle is contained within the cytoplasm of a eukaryotic cell. The second word 'reticulum' means that this is a type of network that is spread within the cell cytoplasm.
The whole endoplasmic reticulum is a continuously connected network of tubules, cisterns, and vesicles that is spread throughout the cytoplasm and is covered with a special membrane. The whole assembly takes up 10% of the total cell volume. Its internal space is called lumen. The bilipid membrane that covers it, allows for transport of molecules into and outside the network. It's a gigantic pipeline that is spread over the whole cytoplasm and is held together by a cytoplasmic skeleton, made up of proteins.
There are two types of endoplasmic reticulum. One is smooth and the other is rough and both of these types are interconvertible. The rough variety has ribosomes attached to the surface, which are sites for protein synthesis, while the smooth one is purely a transport system for the ions and steroids in particular.
Function in Eukaryotic Cells
The function and structure of this organelle varies a bit, according to the type of cell. In the following lines, I talk about the generic functions, irrespective of the cell type.
Proteins are the most crucial of all biological molecules. They make all of a cell's critical functions possible, including photosynthesis in plants and cellular respiration, which produces ATP molecules.
The prime function of endoplasmic reticulum is protein folding. Once proteins are created at ribosomal sites, they need to be folded into the right configurations, for them to carry out their functions properly. The entire folding procedure occurs within its confines. The transportation of the ready protein molecules to their destination is made possible by the association of the reticulum, with what is known as the Golgi apparatus.
The functions of smooth endoplasmic reticulum are different from the rough variety. It plays a different role in every type of eukaryotic cell. Its primary function is that of serving as a site for enzyme action and storing various ions and enzymes for cellular functions.
In muscle cells of the human body, they carry out the function of storage and release of calcium ions, which makes muscle contraction possible. It also carries out the function of transporting proteins to cellular destinations, where they are required. A defect in the reticulum functioning or any damage to it may cause diseases like Alzheimer's.
This organelle plays a big role in protein synthesis, folding, and transport, which is perhaps the most crucial function carried at the cellular level.