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Multiple Choice
Which of the following best describes exocytosis?
A
The passive diffusion of small, nonpolar molecules across the plasma membrane.
B
The process by which cells expel materials to the extracellular environment via vesicles fusing with the plasma membrane.
C
The movement of water across a selectively permeable membrane from an area of low solute concentration to high solute concentration.
D
The process by which cells engulf external substances by forming vesicles from the plasma membrane.
Verified step by step guidance
1
Step 1: Begin by understanding the term 'exocytosis.' Exocytosis is a cellular process where materials are expelled from the cell into the extracellular environment. This is achieved through vesicles that transport substances to the plasma membrane, where they fuse and release their contents outside the cell.
Step 2: Compare the provided options to the definition of exocytosis. Eliminate options that do not align with the process of expelling materials via vesicle fusion with the plasma membrane.
Step 3: Option 1 describes passive diffusion of small, nonpolar molecules, which is unrelated to exocytosis. Passive diffusion does not involve vesicles or active transport.
Step 4: Option 3 describes osmosis, the movement of water across a selectively permeable membrane, which is also unrelated to exocytosis. Osmosis involves water movement, not vesicle-mediated transport.
Step 5: Option 4 describes endocytosis, the process of engulfing external substances by forming vesicles from the plasma membrane. This is the opposite of exocytosis. The correct description of exocytosis is provided in Option 2: 'The process by which cells expel materials to the extracellular environment via vesicles fusing with the plasma membrane.'