The Endomembrane System

Organelles in action

• nuclear envelope

  • controls the flow of materials between the nucleus and cytoplasm

• transport vesciles

  • carries proteins and lipids throughout different parts of the endomembrane system

• lysosomes

  • digest and breaks down waste materials, cellular debris

• endoplasmic reticulum

  • Smooth: synthesizes lipids and regulates calcium levels

  • Rough: synthesizes proteins and modifies them for transport

• golgi apparatus

  • modifies, sorts and packages proteins and lipids for their travel inside or outside the cell

• cell membrane

  • regulates the movement of materials in and out of the cell

The process

• Protein synthesis in Rough ER

  • Ribosomes on the rough endoplasmic reticulum synthesis proteins

  • Once synthesized they enter the rough ER’s lumen (internal space) where they may undergo folding and modifications

    (adding carbohydrate chains)

• Transport from Rough ER to Golgi Apparatus

  • after processing, proteins are packaged into vesciles

  • leave the rough ER and travel to the golgi

• Processing in the Golgi Apparatus

  • the vesciles fuse to the golgi apparatus where further modifications take place.

  • processes proteins and lipids adding tags or groups to determine their destination

• Vescile transport

  • Newly packaged proteins and lipids are enclosed in vesciles and leave the golgi.

  • these vesciles have specific “adress tags” that guide them to different destinations (plasma membrane or other organelles)

• Delivery to final destination

  • Depending on the protein function

    • fuse with the plasma membrane to secrete their contents outside the cell (endocytosis)

    • deliver to other organelles, where the proteins will perform different tasks such as breaking down waste materials

• Lysome function

  • break down waste materials, old organelles, and harmful invaders through enzymes

  • lysomes receive the enzymes through the golgi and help with recylcing and cleaning the cell