Endoplasmic reticulum is derived from the Greek word endo meaning inside, plasmic meaning plasma and reticulum meaning mesh. Endoplasmic reticulum means endoplasmic reticulum. Endoplasmic reticulum is a branched reticular hollow tube located in the cytoplasm of the cell. Small parts of the endoplasmic reticulum break off to form microsomes.
Discovery of endoplasmic reticulum
In 1897, scientist Gorniar observed the lattice-like structure in cells with the help of a light microscope and named them argestoplasm. In 1945, scientist Keith R. Porter and his colleagues Albert Claude and Ernest F. Fullam first discovered it from liver cells. Endoplasmic reticulum was named by scientist Keith R. Porter in 1953. In 1969, scientists Porter, Claude and Fullam described the detailed structure of endoplasmic reticulum from liver cells.
Elongation
Endoplasmic reticulum is found in almost all cells. They are most abundant in the liver, pancreas and endocrine glands. It extends from the nuclear membrane to the cell membrane. It is attached to the nuclear membrane. Mammalian red blood cells, spermatizoa, and sperm lack reticulum.
Types of endoplasmic reticulum
- Smooth endoplasmic reticulum-SER : The endoplasmic reticulum that does not have ribosomes is called smooth endoplasmic reticulum or SER. It synthesizes lipids. It releases calcium during muscle contraction. Smooth endoplasmic reticulum is abundant in adipose cells, testes, adrenal cortex cells, muscle cells and liver cells.
- Rough endoplasmic reticulum-RER : The endoplasmic reticulum that has ribosomes is called rough endoplasmic reticulum or RER. It synthesizes proteins. It stores calcium during muscle contraction. Rough endoplasmic reticulum contains tiny glyoxysome particles. These tiny glyoxysome particles are called microsomes. Pancreatic cells, liver cells, plasma cells and goblet cells have rough endoplasmic reticulum.
Physical structure of endoplasmic reticulum
There are three types of structure of endoplasmic reticulum. These are-
- Lamellar or Cisternae: Endoplasmic reticulum that is long, cylindrical, unbranched and compressed is called cisternae. Their diameter is 40-50 millimicrons. Cisternae contain a glycoprotein called ribophorin. The cisternae are connected to each other with the help of ribophorin.
- Vasicle: The endoplasmic reticulum that looks round or oval or blistered and surrounded by a membrane is called a vesicle. The vesicles are called microsomes. Their diameter is 25-50 mm. Vesicles are abundant in protein-synthesizing pancreatic cells.
- Tubules: The endoplasmic reticulum which is long, cylindrical and branched is called tubules. Their diameter is 50-190 millimicrons. It stays connected. They have no ribosomes.
Chemical composition
The main chemical components of endoplasmic reticulum are proteins and lipids. It contains protein 60-70% and lipid 30-40%. Asymmetric lattice contains ATP and glyoxysomes. Besides, it contains 15 types of enzymes and co-enzymes. Enzymes are – glucose 6 phosphate, NADH diaphorase, active ATP-ase, glycosyl transferase, NADH cytochrome reductase, stearase, esterase, nucleotide diphosphatase, peptidase, fatty acyl CoA dehydrogenase etc.
Function of Endoplasmic Reticulum
- Formation of intracellular skeleton: Endoplasmic reticulum extends like a net inside the cell and forms the intracellular skeleton. It provides cell strength.
- Structure of the body: Endoplasmic reticulum acts as the structure of protoplasm.
- Speed of reaction: It increases the speed of chemical reaction. It increases biochemical activity in cells.
- Substance transport: Endoplasmic reticulum forms the intracellular transport system. It acts as a transport pathway for various substances. It plays a major role in the transport of proteins produced in ribosomes.
- Hydroxylating: Different types of drugs and toxic substances enter the body. The endoplasmic reticulum inactivates drugs and toxins in the hydroxylating process. As a result, the body gets rid of toxins.
- Muscle contraction-dilation: It helps in muscle contraction-dilation.
- Cell wall formation: It makes cellulose. Cellulose participates in making cell walls.
- Chemical production: It produces lipids, hormones, phospholipids, steroids, glycoproteins, glycogen, vitamins and insulin.
- Organelle formation: Endoplasmic reticulum participates in the formation of various organelles of the cell.
- Protein synthesis: It synthesizes proteins. Proteins make up the body of organisms.
- Cell distribution: The endoplasmic reticulum holds the cell membrane in place and distributes it uniformly.
- As a container: It acts as a container for ribosomes and glyoxysomes.
- Nuclear membrane formation: It participates in nuclear membrane formation in telophase.
- Glucose production: Glucose is produced from glycogen in the process of glycogenolysis.
- Formation of Spherosomes: Spherosomes are formed from smooth endoplasmic reticulum.
- As a carrier: It acts as a carrier of proteins and lipids.
- Neutralization: It neutralizes various toxic substances entering the cells.