Endomembrane System Notes

Endomembrane System

• The endomembrane system comprises all cell parts with a membrane where the membrane moves from one location to another.
• It includes organelles where membrane lipids are incorporated from one to another. If membrane lipids get incorporated into the next organelle, it's part of this system.

Components

• Endoplasmic Reticulum (ER):
  • The starting point for membrane movement in the system.
• Golgi Body:
  • Receives components that move from the endoplasmic reticulum.
• Vesicles:
  • Transport lipids and proteins between organelles.
• Endosomes:
  • Formed from vesicles.
• Lysosomes:
  • Derived from endosomes.
• Plasma Membrane:
  • The endomembrane system gets incorporated into the plasma membrane.

Exclusions

• Peroxisomes:
  • Not part of the endomembrane system because their membranes do not originate from the ER via vesicle fusion in the standard way; however, they are discussed with the endomembrane system due to the lack of a better classification.
• Nuclear Membrane:
  • Although the nucleus has a membrane, it is not part of the endomembrane system because vesicles that originate from the ER do not fuse with it.
• Mitochondrial Membrane:
  • Excluded because vesicles do not fuse with it.

Key Principle

• The endomembrane system is defined by the movement and fusion of vesicles originating from the endoplasmic reticulum to various cellular components.