A eukaryotic cell needs to internalize a large protein complex from its extracellular environment or release a neurotransmitter into the synaptic cleft. Which of the following statements accurately describes the general mechanism for these cellular transport processes?
Show answer and explanation
The answer
Correct answer: B. These processes involve the formation of membrane-bound vesicles that fuse with the plasma membrane to transport bulk materials.
Tested concept: Endocytosis and exocytosis
Explanation
Endocytosis and exocytosis are active transport mechanisms that involve the formation and fusion of membrane-bound vesicles. Endocytosis brings substances into the cell by engulfing them in a vesicle, while exocytosis releases substances from the cell by fusing a vesicle with the plasma membrane. This allows for the transport of large molecules or bulk materials that cannot pass through protein channels or carriers. The option stating that these processes primarily utilize transmembrane protein channels is incorrect because channels are for smaller molecules and ions. The option stating that both endocytosis and exocytosis are forms of passive transport is incorrect because both processes are active transport, requiring energy, and do not rely on electrochemical gradients for their primary driving force. The option claiming they move substances against their electrochemical gradients is incorrect because while endocytosis and exocytosis are active transport, they do not necessarily move substances against an electrochemical gradient, but rather transport large amounts of material or large molecules via vesicles.
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