Sequence of Exocytosis Events

Steps:

• Glycoproteins in the Golgi are enclosed by folding membranes, initiating vesicle formation.
• This folding process creates a secretory vesicle containing the glycoproteins.
• The formed secretory vesicle then transports to the cell membrane.
• The vesicle binds and fuses with the plasma membrane, releasing contents outside the cell.

Why B is correct:

• B (1→3→2) matches the secretory pathway definition, where Golgi packaging (1) forms vesicles (3) before plasma membrane fusion (2) for exocytosis.

Why the others are wrong:

• A: Places fusion (2) before vesicle formation (3), impossible without a vesicle.
• C: Begins with fusion (2), which requires prior vesicle creation.
• D: Starts with vesicle formation (3) before Golgi packaging (1), reversing the packaging sequence.

Final answer: B