Lecture 8

• Endomembrane system


  Inside the cell

  Manufactures, sorts and distributes molecules

  Physical continuity or vesicle transfer between components

  Components:

  • Golgi Apparatus
  • Vacuole ( only in plant cells)
  • Endoplasmic reticulum
  • Plasma membrane
  • Nuclear envelope
• Vacuoles

  Stores ions and organic compounds

  Derived from ER and Golgi

  Hydrolytic enzymes
• Secreted Proteins

  Secreted proteins have a signal peptide at the start, which tells the cell where to send them

  The signal peptide binds to a molecule called SRP, stopping protein reproduction temporarily

  The ribosome, with the signal peptide, moves to the rough ER, where protein production continues

  After production, the proteins goes to the Golgi, where sugars may be added

  Finally, the protein moves in vesicles to the cell membrane for secretion or use in the membrane
• Non-Secreted Proteins


  Made in the cytoplasm

  Stays in the cell
• Signal Peptide 


  Tells the signal recognition particle If the protein being made is destined for secretion or not

  Binds with ER lumen on the rough ER
• Signal Recognition Particle

  Recognises signal peptide

  Stops translation (if its a secreted protein)

  Takes ribosome to the rough ER
• Process of Glycosylation

  Glycosylation is the process of adding sugar molecules to proteins or lipids. It happens in the Golgi apparatus or cells. During glycosylation:

  • Sugars are attached to specific sites on proteins and lipids
  • Enzymes in the Golgi modify the attached sugars, Creating different structures
  • These sugars modifications are crucial for protein folding, Stability and cell communication
  • The modified proteins or lipids are then sent tot here final destination inside or outside the cell