Choose the answer that best completes the following analogy: Diffusion is to as endocytosis is to
A.
filtration; phagocytosis
B.
osmosis; pinocytosis
C.
solutes; fluid
D.
gradient; chemical energy
The Correct Answer and Explanation is:
The correct answer is B. osmosis; pinocytosis.
Explanation:
In biological processes, diffusion and endocytosis are mechanisms by which substances move across cell membranes, but they operate differently. Let’s break down the analogy.
- Diffusion: Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. This process occurs passively, meaning it doesn’t require energy. Diffusion is essential for moving solutes like gases (oxygen and carbon dioxide) and small molecules across membranes. In this analogy, diffusion is compared to osmosis. Osmosis is a special type of diffusion that involves the movement of water across a semipermeable membrane. Just like diffusion, osmosis moves from an area of higher concentration (water in this case) to a lower concentration but involves water instead of solutes. Therefore, osmosis is the correct analogy for diffusion, as both processes are passive and involve movement from high to low concentrations.
- Endocytosis: Endocytosis is the process by which cells engulf substances from the external environment into the cell by wrapping them in a section of the cell membrane. Unlike diffusion, endocytosis requires energy in the form of ATP, making it an active process. Endocytosis is further divided into types:
- Phagocytosis: Engulfing large particles, such as bacteria or debris.
- Pinocytosis: Ingesting small particles and liquids.
Thus, the analogy correctly pairs osmosis (a type of diffusion) with pinocytosis (a type of endocytosis). The processes share common features in their respective categories (passive vs. active transport).