What's the difference between an early and late endosome?

Early Endosomes:

• The main sorting machine of the endocytic pathway
• Relatively small
• Often located in the periphery of the cytoplasm near the plasma membrane
• Tubular and vacuolar in composition
• Weakly acidic (pH 5.9-6.8)
• Low Ca2+ concentration
• Lack acid hydrolases

Late Endosomes:

• May fuse with lysosomes to degrade cargo
• Round or oval-shaped
• Shuttle between peripheral cytoplasm and perinuclear area
• Lumen often contains variously sized vesicles
• More acidic than early endosomes (pH 4.9-6.0)
• Increased Ca2+ concentration compared to early endosomes
• Replete with acid hydrolases