Endocytosis Involves Energy-Dependent Vesicle Formation

Steps:

• Define endocytosis as the cellular process of taking in substances by enclosing them in a membrane-bound vesicle.
• Identify key features: it moves materials into the cell and requires ATP energy as an active transport mechanism.
• Evaluate choices: A and B describe carrier-mediated transport (active or passive), not vesicle-based; D omits energy requirement.
• Select C as it matches the definition of endocytosis precisely.

Why C is correct:

• Endocytosis is defined as active transport where cells engulf particles or fluids into vesicles, requiring energy (ATP) to deform the membrane and form the vesicle.

Why the others are wrong:

• A describes active transport via carrier proteins, like the sodium-potassium pump, not vesicles.
• B describes facilitated diffusion, a passive process down the gradient using carriers, without vesicles.
• D describes passive vesicle transport, but endocytosis specifically requires energy, unlike exocytosis in some contexts.

Final answer: C