STD-11 UNIT-3 CHA-8
CELL : STRUCTURE AND FUNCTIONS
Function of Endoplasmic Reticulum
Common Functions of ER- It provides a large surface inside the cell for various physiological activities.
- It functions as cytoskeleton or intracellular and ultrastructural skeletal framework by providing mechanical support to colloidal cytoplasmic matrix.
- Endoplasmic reticulum keeps the various organelles in their position.
- Endoplasmic reticulum (as desmotubules) controls movement of materials between two adjacent protoplasts through plasmodesmata.
- Endoplasmic reticulum acts as a means of quick intracellular transport.
- In cells, endoplasmic reticulum conducts information from cell exterior to inside and from one part of the cell to another, e.g. , cytoplasm to nucleus and vice versa.
- It provides membranes to nuclear envelope after telophase.
- It provides precursors of different secretory substances Golgi apparatus.
- It gives membranes to Golgi apparatus for the formation of vesicles and lysosomes.
- It gives rise to vacuoles.
- Complexing of proteins and lipids to form lipoproteins occur in ER.
- The membranes of endoplasmic reticulum contain a number of enzymes (e.g. , ATPase, reductases, dehydrogenases, phosphatases) for various metabolic activities and cytochromes that take part in electron transport.
- It contains SRP receptors or ribophorins for providing attachment to ribosomes.
- RER provides a large surface area to ribosomes.
- It bears enzymes in the region of pores for modifying polypeptides synthesised by attached ribosomes , e.g .. glycosylation.
- lt synthesises serum proteins , membrane proteins and a number of other proteins . intracellular use as well as secretion.
- Proteins and enzymes synthesised by ribosomes enter the channels of RER both for
- It provides enzyme precursors for the formation of lysosomes by Golgi complex.
- SER can develop from RER by discarding ribosomes.
- It is responsible for synthesis of fats inside the cells of adipose tissue, formation of sphaerosomes, synthesis of glycogen as well as glycogenolysis (hydrolysis of glycogen) in liver cells (for this, SER possesses enzyme bodies called glycosomes) synthesis of ascorbic acid, synthesis of sterols and steroid hormones as in the interstitial cells of testis and ovary and formation of visual pigments from vitamin A in retinal cells.
- As sarcoplasmic reticulum, it stores Ca2 + for release during muscle contraction.
- It takes part in detoxification of toxic chemicals with the help of cytochrome P - 450.
- Synthetic products of RER pass on to Golgi complex through SER .
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