Pinocytosis is a type of:

• A. facilitated diffusion
• B. endocytosis
• C. exocytosis
• D. osmosis

Answer: (B)

Verified step by step guidance

1. Understand the concept of pinocytosis: Pinocytosis is a cellular process where the cell engulfs extracellular fluid and dissolved substances into small vesicles. It is often referred to as 'cell drinking.'
2. Recognize that pinocytosis is an active transport mechanism: Unlike passive processes such as facilitated diffusion or osmosis, pinocytosis requires energy (ATP) because the cell actively forms vesicles to internalize substances.
3. Differentiate between endocytosis and exocytosis: Endocytosis involves the intake of substances into the cell, while exocytosis is the process of expelling substances out of the cell. Pinocytosis falls under the category of endocytosis.
4. Eliminate incorrect options: Facilitated diffusion and osmosis are passive transport mechanisms that do not involve vesicle formation or energy expenditure, making them incorrect answers.
5. Conclude that pinocytosis is a type of endocytosis, as it involves the active transport of extracellular fluid into the cell via vesicle formation.