Answer to Question #122180 in Biochemistry for amina

Question

Function of Endoplasmic reticulum

Answer 1

There are mainly two types of endoplasmic reticulum namely;

1)     Smooth Endoplasmic Reticulum.

2)     Rough Endoplasmic Reticulum.

1. Smooth Endoplasmic Reticulum

• They are also known as the agranular endoplasmic reticulum.
• It have smooth walls since the ribosomes are not attached to its membranes.
• It is oftenly found in cells, which are involved in the metabolism of lipids and glycogen. Example adipose cells, interstitial cells, glycogen storing cells of the liver, conduction fibers of heart, spermatocytes, and leucocytes.

2. Rough Endoplasmic Reticulum

• It have rough walls since the ribosomes remain attached to its membranes.
• Rough Endoplasmic Reticulum (RER) contains certain ribosome known as ribophorins I and II, to which are attached the ribosomes while engaged in polypeptide synthesis.
• The rough type of endoplasmic reticulum is found abundantly in those cells which are active in protein syntheses such as pancreatic cells, plasma cells, goblet cells, and liver cells.

FUNCTIONS OF ENDOPLASMIC RETICULUM.

1)      Functions of smooth ER include lipid metabolism (both catabolism and anabolism; they synthesize a variety of phospholipids, cholesterol, and steroids).

2)      Glycogenolysis (degradation of glycogen; glycogen being polymerized in the cytosol).

3)      Drug detoxification (by the help of the cytochrome P-450).

4)      The endoplasmic reticulum provides an ultrastructural skeletal framework to the cell and gives mechanical support to the colloidal cytoplasmic matrix.

5)      The exchange of molecules by the process of osmosis, diffusion and active transport occurs through the membranes of the endoplasmic reticulum.

6)      The endoplasmic reticulum is the main component of the endomembrane system, also called the cytoplasmic vacuolar system or cytocavity network.

7)      The endoplasmic membranes contain many enzymes that perform various synthetic and metabolic activities. Further, the endoplasmic reticulum provides an increased surface for various enzymatic reactions.

8)      The endoplasmic reticulum acts as an intracellular circulatory or transporting system.

9)      As a growing secretory polypeptide emerges from the ribosome, it passes through the RER membrane and gets accumulated in the lumen of RER. RER pinches off certain tiny protein-filled vesicles which ultimately get fused to Golgi.

10)  The ER membranes are found to conduct intra-cellular impulses. For example, the sarcoplasmic reticulum transmits impulses from the surface membrane into the deep region of the muscle fibers.

11)  The ER membranes form the new nuclear envelope after each nuclear division.

12)  The SER contains several key enzymes that catalyze the synthesis of cholesterol which is also a precursor substance for the biosynthesis of two types of compounds the steroid hormones and bile acids.