Which of the following statements correctly describes some aspect of exocytosis or endocytosis?

• A. Exocytosis is the process by which cells internalize molecules by engulfing them in a vesicle.
• B. Exocytosis involves the engulfing of external substances into the cell.
• C. Endocytosis involves the fusion of vesicles with the plasma membrane to release contents outside the cell.
• D. Endocytosis is the process by which cells internalize molecules by engulfing them in a vesicle.

Answer: (D)

Verified step by step guidance

1. Understand the definitions: Exocytosis and endocytosis are cellular processes used to transport materials. Exocytosis is the process by which cells expel materials, while endocytosis is the process by which cells internalize materials.
2. Analyze the first statement: 'Exocytosis is the process by which cells internalize molecules by engulfing them in a vesicle.' This statement incorrectly describes exocytosis, as it is actually describing endocytosis.
3. Analyze the second statement: 'Exocytosis involves the engulfing of external substances into the cell.' This statement is incorrect because exocytosis is about expelling substances from the cell, not engulfing them.
4. Analyze the third statement: 'Endocytosis involves the fusion of vesicles with the plasma membrane to release contents outside the cell.' This statement incorrectly describes exocytosis, as endocytosis is about internalizing substances.
5. Identify the correct statement: 'Endocytosis is the process by which cells internalize molecules by engulfing them in a vesicle.' This statement correctly describes endocytosis, where the cell membrane engulfs external materials to form a vesicle that is brought into the cell.