Endoplasmic reticulum class IX

Class IX Science Chapter->The Fundamental Unit of Life

1. ENDOPLASMIC RETICULUM DONE BY :- S.Durgashree IX-A KENDRIYA VIDYALAYA KARAIKUDI

2. Discovered by Belgian biologist Albert Claude (1899-1983). Used the newly developed electron microscope to explore the interior of cells and along with his associate Keith Porter in 1945 observed the presence of a “lace-work structure.” WHO DISCOVERED THE ER ?

3. Rough ER appears as lumpy sheets of folded membranes. The lumps are the ribosome. They are not permanently attached, adhering only when there is protein manufacturing work to be done. Smooth ER which isn't coated with ribosome's looks like smooth tubes. HOW DOES THE ER LOOKS LIKE ?

4. No specific base or point in a cell, as it extends a network of membranes, tubules vesicles, and sacs throughout the cell. ER membranes are folded and stacked on top of each other and connected to the nucleus. Rough ER with ribosomes attached is closest to the nucleus. WHERE IS THE ER LOCATED ?

5. Endoplasmic - “within the cytoplasm”. Reticulum - Latin for “a little net”. -> Extensive network of folded membranes that extends from the nuclear envelope to which it is connected, throughout the cytoplasm. -> Divided into two sub-compartments, rough ER and smooth ER. ENDOPLASMIC RETICULUM

6. -> Defined by the presence of ribosomes bound to its cytosolic surface. -> Typically composed of a network of flattened sacs (cisternae). ROUGH ER

7. ->Continuous with the outer membrane of the nuclear envelope, which also bears ribosomes on its cytosolic surface. ROUGH ER

8. Secrete large quantities of proteins, such as the : (a) Acinar cells of the pancreas FUNCTIONS OF ROUGH ER

9. (b) Mucus secreting cells of the lining of the digestive tract. FUNCTIONS OF THE ROUGH ER

10. Rough ER is the starting point of the biosynthetic pathways of: Proteins Carbohydrate chains Phospholipids that journey through the membranous compartments of the cell. FUNCTIONS OF THE ROUGH ER

11. Lacks associated ribosomes. Membranous elements are highly curved and tubular, forming an interconnecting system of pipelines curving through the cytoplasm. SMOOTH ER

12. Extensively developed in a number of cell types, including those of skeletal muscle, kidney tubules, and steroid-producing endocrine glands FIGURE 1. The smooth ER (SER). Electron micrograph of a Leydig cell from the testis showing the extensive smooth ER where steroid hormones are synthesized. SMOOTH ER

13. Synthesis of fatty acids and steroid hormones, such as estrogens and testosterone. Detoxification in the liver of a wide variety of organic compounds, including barbiturates and ethanol. Sequestering calcium ions within the cytoplasm of cells. FUNCTIONS OF THE SMOOTH ER

14. Ribosomes on its outer surface. Not associated with ribosomes. Site of synthesis of proteins destined for secretion . Involved in lipid metabolism. ROUGH ER vs. SMOOTH ER

15. ON MEMBRANE - BOUND RIBOSOMES: a. Secreted proteins b. Integral membrane proteins c. Soluble proteins in ER, Golgi complex, lysosomes, endosomes, vesicles and plant vacuoles ON FREE RIBOSOMES: a. Cytosolic proteins b. Peripheral proteins c. Proteins transported to the nucleus d. Proteins to be incorporated in peroxisomes, chloroplasts and mitochondria PROTEIN SYNTHESIS

16. As each protein is synthesized in the rough ER, it becomes inserted into the lipid bilayer in a predictable orientation determined by its amino acid sequence. This orientation is maintained throughout its travels in the endomembrane system, as illustrated in this figure. MEMBRANE BIOSYNTHESIS IN THE ER

17. I hope that you would have gained knowledge from this power point presentation….

18. THANK YOU