Discovery First observe by Garnier (1897) and named it as ergastoplasm. Ultra structure given by Porter, Claude and Fullam (1945). Term “endoplasmic reticulum” coined by K.R. Porter (1953).

Definition “Well developed electron microscopic network of inter connected cisternae, tubules and vesicles present throughout the cytoplasm, especially in the endoplasm”.

Types of endoplasmic reticulum On the basis of metabolic state of cells and absence or presence of ribosome, or is of two types:- Rough endoplasmic reticulum. Smooth endoplasmic reticulum.

Ultra structure

Chemical composition Cytochemically studies showed that there are more lipids in SER than RER. SER is with more sphingomyelin and cholesterol. In RER, about 30 types of proteins have been identified.

Enzymes Synthetases. NADH- Cytochrome C- reductase. Glucose-6-phosphatase. Mg++-activated ATPase. Nucleotide diphosphatase.

Inter relationship between different membranes of the cell

Difference between SER and RER Ribosomes absent. Present near the cell membrane. Formed of tubules. Found in lipid forming cells e.g: Adipocytes, interstitial cells, adrenal cortical cells, Leucocytes, Retinal cells. RER Ribosomes present. Present near the nucleus. Formed of cisternae. Found in protein forming cells e.g: Acinal cells, goblet cells, plasma cells, Nissl’s granules, endocrine cells etc.

Function of RER Protein synthesis. Formation of nuclear envelop. Formation of SER. Formation of transition vesicles. RER packages the polypeptides into the protein.

Function of SER Lipid synthesis. Synthesis of steroid hormones. Glycogenolysis . Nerve impulse conduction. Detoxification of drugs. Synthesis of Ascorbic acid. Fat Oxidation.

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