Some consider osmosis a special case of diffusion because it only involves the movement of what substance?
A. Oxygen B. Salt C. Water D. Carbon dioxide
The correct answer and explanation is:
The correct answer is C. Water.
Osmosis is indeed considered a special case of diffusion because it specifically refers to the movement of water molecules across a semi-permeable membrane. While diffusion in general involves the movement of molecules from an area of higher concentration to an area of lower concentration, osmosis is a type of diffusion that focuses solely on water. It occurs when water molecules move from an area of low solute concentration (high water concentration) to an area of high solute concentration (low water concentration) across a membrane that is selectively permeable to water but not to most solutes.
The semi-permeable membrane allows only certain molecules to pass through, and in the case of osmosis, it typically restricts solutes like salt or sugars but permits the movement of water. Osmosis plays a critical role in biological systems, particularly in the maintenance of cell integrity. For example, cells rely on osmosis to maintain their shape and function by regulating the balance of water inside and outside of the cell. If too much water enters the cell (hypotonic solution), the cell may burst, whereas if too little water enters (hypertonic solution), the cell may shrink.
In contrast to regular diffusion, which can involve gases or solutes like oxygen and carbon dioxide, osmosis is specifically concerned with water. It is essential for many physiological processes, such as nutrient absorption in the intestines and the regulation of blood pressure in the kidneys. Osmosis is also a key mechanism in plant cells, helping to transport water from roots to leaves, ensuring that plants can carry out vital processes like photosynthesis.