Endoplasmic Reticulum: Structure, Types and Functions

Every organism’s basic structural and functional units are cells. They are divided into two categories: prokaryotic and eukaryotic. Prokaryotic cells can be found in species belonging to the Bacteria and Archaea domains. Eukaryotic cells, on the other hand, are found in fungi, animals and plants. There are some structural and functional distinctions between these two types of cells. The membrane-bound cell organelles including the endoplasmic reticulum are not found in the prokaryotic cells. Nonetheless, eukaryotic and prokaryotic cells share several fundamental characteristics, such as.

1. The plasma membrane, also commonly known as the cell membrane, separates the cells. It protects the cells by acting as a selective barrier.
2. Within the cells, there is a jelly-like natural substance, called cytosol, which performs several activities.
3. DNA can be found in the chromosomes of a cell. This section is involved in the expression of traits and heredity.
4. Ribosomes are found in all cells and are responsible for the production of the protein that is essential for cellular functioning.

It is necessary to understand ribosomes before understanding the endoplasmic reticulum. Ribosomes are regarded as protein factories since they are involved in the protein synthesis process. Ribosomes are biological components or complexes that are composed of ribosomal RNA and proteins. They are extremely small, measuring only around 25 nanometres in diameter. The attached ribosomes are connected to the exterior of the endoplasmic reticulum or nuclear envelope to make proteins, while free ribosomes are suspended in the cytosol. In general, attached ribosomes produce proteins that are intended for incorporation into membranes, bundling into cellular organelles like lysosomes, and exportation.

Endoplasmic reticulum:

The ER stands for endoplasmic reticulum. The name is made up of two words: endoplasmic means “inside the cytoplasm,” and reticulum means “little net” in Latin. In many eukaryotic cells, the endoplasmic reticulum is a huge array of membranes that passes through all the cytoplasm, accounting for nearly half of the total membrane.

Endoplasmic reticulum structure:

1. A network of sacs and tubules is found in them. This network is known as cisternae. The name cisternae is derived from the Latin word cisterna, which refers to liquid storage.
2. The endoplasmic reticulum lumen, also known as the cisternal space, is a canal generated by the endoplasmic reticulum membrane that separates the endoplasmic reticulum structure’s internal compartment from the cytoplasm.
3. There is a constant space between the two membranes of the nuclear envelope with the endoplasmic reticulum lumen because the endoplasmic reticulum membrane is consistent with the nuclear envelope membrane.
4. The flattened compartments or sacs generated in this manner provide space for processes to occur within them. The sacs can be merged to create the reticulum, which is a complete system. As a result, the endoplasmic reticulum is connected to the nuclear envelope’s outer membrane.

Types of endoplasmic reticulum: The following are the two types of endoplasmic reticulum:

1. Rough endoplasmic reticulum (RER): It is a type of endoplasmic reticulum that is, it gets its name from the fact that it is coated in ribosomes, which are small organelles. They are made up of two subunits, one large and one smaller, which may be observed at extremely high magnifications.
2. Smooth endoplasmic reticulum (SER): It is a type of endoplasmic reticulum in which ribosomes are not present. It also serves a very different purpose. It produces cholesterol and the reproductive hormones oestrogen and testosterone, as well as lipids and steroids.

 

Functions of Endoplasmic Reticulum:

The functions of the smooth endoplasmic reticulum are as follows:

• The smooth endoplasmic reticulum’s enzymes play a critical role in the production of lipids such as oils, steroids, and new membrane phospholipids

• Other smooth endoplasmic reticulum enzymes, particularly in liver cells, aid in the detoxification of medicines and toxins

• Calcium ions are also stored in the smooth endoplasmic reticulum

The rough endoplasmic reticulum’s functions are as follows :–

• They play a function in protein synthesis since they have connected ribosomes.

• Rough endoplasmic reticulum aids in the separation of the produced element from the other cell components as well as their delivery through transport vesicles.
• They produce a membrane factory that contributes to the creation of transport vesicles that convey proteins in the cytoplasm, among other things.