Sunday, 24 March 2013

Cell Organelles

Brief introduction to cell orgenelles :

                     They are bounded by two membranes with the inner one extensively folded.Enzymes in inner mitochondrial membrane and central matrix carryout terminal stages of sugar and lipid oxidation coupled ATP synthesis.That's why it is called as "power house of the cell".

Chloroplast(in plant cell):
                                     Site responsible for Photosynthesis.It is surrounded by an inner and outer membrane,complex system of thylakoid membranes in their interior contains the pigments and enzymes responsible for absorption of light and produce ATP.

            It consist of inner and outer membrane.Also consist of nucleopores responsible for materials to pass between the nucleus and cytosol. Outer membranes are the continuation of rough endoplasmic reticulum.The nuclear membrane mimics the function of plasma membrane about nucleus. The nucleus mainly contains DNA organized into linear structure called Chromosomes.

Endo plasmic reticulum(ER):
                                   These are the network of interconnected membranes.It's of two types.(1) Rough Endoplasmic reticulum. (2) Smooth Endoplasmic Reticulum.

Rough ER: 
                 Ribosomes are present in theon the surface here.It is responsible for protein synthesis in a cell.These are suborganelles in which amino acids are actually bound together to form proteins.There are spaces in between folds of ER membrane and called as Cisternae.

Smooth ER:
                  In this type of ER,there is no ribosomes(absence) present in the surface.

Golgi bodies or Golgi Apparatus or Dictyosomes:
                                                                          It is a series of flattened sacs usually curled at the edges.Proteins which are formed on the ribosomes of rough ER are processed in golgi apparatus.After processing,the final product is released from Golgi apparatus(GA).At this time GA buges and breaks away to form vesicles known as secretory vesicles.

              Vacuoles forms about 75% of the plant cells.In the vacuole only the plant cell stores nutrients as well as toxic wastes.If the pressure increases within vacuoles results in increase in size of the plant cell(becomes swollen).If this pressure gets increased the cell nay bursts.

                 These are found in all cells(both prokayotic and  eukaryotic) except in sperm cells and RBC's.In eukaryotic cells they occur freely in the cytoplasm and also found attached to the outer surface of rough ER.These are the sites for Protein Synthesis.

Plasma membrane:
                            In all cells the plasma membrane has several functions to perform. These include transporting nutrients into and metabolites out of the cell. It is formed of lipids and proteins.

                   These are spherical bodies bound by single membrane.These are the sites of glyoxylate cycle in plants.

Cell wall:
             Cell wall present only in plant cell.It has three parts namely 1.middle lamella 2. Primary wall 3.Secondary wall.It gives definite shape to the cell.


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