Rucete ✏ Campbell Biology In a Nutshell
Unit 2 THE CELL — Concept 6.4 The Endomembrane System Regulates Protein Traffic and Performs Metabolic Functions in the Cell
The endomembrane system is a complex group of interrelated organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins. This system compartmentalizes the cell, allowing specific functions to occur within distinct areas.
1. Components of the Endomembrane System
Nuclear Envelope: Encloses the nucleus, separating it from the cytoplasm.
Endoplasmic Reticulum (ER):
Rough ER: Studded with ribosomes; synthesizes proteins for secretion or membranes.
Smooth ER: Lacks ribosomes; synthesizes lipids, detoxifies substances, and stores calcium.
Golgi Apparatus: Modifies, sorts, and ships proteins and lipids from the ER.
Lysosomes: Digestive organelles that break down macromolecules, damaged organelles, and invaders.
Vacuoles:
In plants: large central vacuole for storage and structure
In animals: smaller vesicles with varied functions
Plasma Membrane: Controls what enters and exits the cell; participates in vesicle fusion and secretion.
2. Functions of the Endomembrane System
Protein and Lipid Processing: ER makes them, Golgi modifies and ships them.
Detoxification: Smooth ER enzymes neutralize drugs and toxins.
Digestion and Recycling: Lysosomes digest internal and external materials.
Storage and Structure: Vacuoles manage storage and maintain turgor pressure in plants.
Efficient Compartmentalization: Allows incompatible processes to occur in separate spaces.
3. Interconnected by Vesicles
Organelles communicate by vesicle trafficking—tiny membrane sacs that bud off from one organelle and fuse with another. This ensures seamless transport of molecules throughout the cell.
In a Nutshell
The endomembrane system organizes the cell into functional compartments.
It includes the nuclear envelope, ER, Golgi, lysosomes, vacuoles, and plasma membrane.
Functions include protein synthesis, lipid metabolism, detoxification, digestion, and secretion.
Vesicles allow coordination and communication between organelles—like a cellular delivery service.