Structure of an epithelial cell 2

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  • Created by: Jasmin
  • Created on: 19-10-13 16:17
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  • Structure of an epithelial cell...
    • ENDOPLASMIC RETICULUM: 3D - like membranes spreading through cytoplasm of cells
      • Membranes enclose flattened sacs called cristae
      • Rough Endoplasmic Reticulum (RER) has ribosomes present on outer surfaces of membrane
        • Functions
          • Provide large SA for synthesis of proteins and glycoproteins
          • Provide pathway for transport of materials, esp proteins, throughout cell
      • Smooth Endoplasmic Reticulum (SER): lacks ribosomes on surface and is more tubular in appearance
        • Functions
          • Synthesise, store and transport lipids
          • Synthesise, store and transport carbohydrates
      • Stack of membranes that make up flattened sacs with small rounded hollow structures called vesicles
      • Proteins, lipids produced by ER passed through GA
      • Golgi modifies proteins adding non protein components e.g. carbohydrates to them
      • Modified proteins, lipids transported in vesicles which are regularly pinched off from ends of Golgi cristemae
      • Vesicles move to cell surface, where they fuse with membrane and release contents to the outside
      • Functions
        • Add carbohydrate to proteins to form glycoproteins
        • Produce secretory enzymes
        • Secrete carbohydrates
        • Transport, modify and store lipids
        • Form lysosomes
    • LYSOSOMES: formed when vesicles produced by GA contain enzymes e.g. protease, lipase
      • Fuctions
        • Break down material ingested by phagocytic cells e.g. white blood cells
        • Release enzymes to outside of cell to destroy material around the cell
        • Digest worn out organelles so useful chemicals are made of can be reused
        • Completely break down cells after have died (autolysis)
    • RIBOSOMES: small cytoplasmic granules found in all cells
      • Important in protein synthesis
      • 2 subunits - one large and one small each of which contains ribosomal RNA and protein
      • 80S type - eukaryotic, 70S type - prokaryotic slightly smaller
    • MICROVILLI: finger like projections that increase SA to allow more efficient absorption


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