Ribosomes, golgi apparatus, lysosomes

Ribosomes, golgi apparatus, lysosomes

1. RIBOSOMES, GOLGI APPARATUS, LYSOSOMES Nov 28

2. RIBOSOMES: Discovered by PALADE (1955). Function: Protein synthesis. Structure: Globular or granular. Occurrence: In the cytoplasm and on Endoplasmic Reticulum. Composition: Eukaryotic ribosomes are made up of equal amount (50%) of RNA and Protein (50%) also called riboproteins that’s why. Subunits: it has two sub-units one is larger and one smaller. Larger subunit: Sediments at 60S (Svedberg unit of sedimentation)

3. Smaller sub-unit: It sediments on 40S When both subunits fuse they result in 80S ribosome particle. The attachment of both sub-units is controlled by Mg ions. POLYSOMES: ribosomes attached to mRNA for protein production. Formation: Inside nucleolus and from here they are transported to cytoplasm or ER through nuclear pore.

4. GOLGI APPRATUS: Discovered by Golgi in 1898. Found only in Eukaryotic cells Consist of: stacks of flat membranes sacs called cisternae. GOLGI Complex: cisternae with associated vesicle. WHAT IS GOLGI APPARATUS? It is a complex system of inter-connected tubules around the stacks.

5. PRODUCTION OF GOLGI APPARATUS : Cisternae are continuously formed by fusion of vesicles, which are derived by budding in Smooth Endoplasmic Reticulum. FORMING FACE: The outer convex surface of cisternae Maturing FACE: The inner concave surface of cisternae FUNCTION OF GOLGI COMPLEX: Involved in cell secretions. Use to pack and transport the cellular material like proteins made in ribosomes out of the cell by forming a covering or membrane or vesicle around them to protect them form lysosomal activities. Example: Pancreas secretes food digesting enzymes and these enzymes are packed and transported out of cell by golgi bodies. Protein and Lipid modification: It can modify lipids or protein by adding carbohydrates in them for their protection e.g converts proteins into Glycoprotein or Lipoprotein before it’s secretion.

6. LYSOSOMES: Discovered by De Duve in 1949. Lyso means splitting and some means body. Present only in Eukaryotic cells. FUNCTION: Phagocytosis: if any foreign particle enters inside cell lysosome destroy it converting in digest-able or small sized molecules. Great in number in those animal cells which do phagocytosis e.g. white blood cells.

7. STRUCTURE: Have single membrane. Are just simple sacs containing acid phosphatase and hydrolytic enzymes. Primary Lysosome: Newly produced lysosomes. Secondary Lysosome: Lysosome that contains foreign particle or particle to be digested . Produced in Rough Endoplasmic Reticulum and then bound by lysosomal membrane in golgi complex

8. FUNCTION: Phagocytosis Autophagy: it can eat the cell’s organelles( which are old or non-functional) It help in recycling of cellular organelles ABNORMALITIES: If not developed properly can do un-controlled autophagy resulting in cellular damage.

9. STORAGE DISEASES: Lysosome help cell to use it’s stored components by breaking them into simple molecules. But if lysosomes develop abnormally or do not function properly then: GLYCOGENESISTYPE II: Type of storage disease in which stored glycogen in the muscles or liver cell remain stored due to absence of functional lysosomes responsible for digesting glycogen and converting it into glucose. TAY-SACH’S DISEASE : It occurs in brain cells due to absence of lipid digesting lysosomes in brain and patient become mentally retarded.