Explain how osmosis works and what is actually moving across the membrane and in what direction.
The correct answer and explanation is:
Osmosis is a process in which water molecules move across a selectively permeable membrane, from a region of lower solute concentration to a region of higher solute concentration. The selectively permeable membrane allows only certain molecules, like water, to pass through, while blocking others, such as larger solute molecules.
The driving force behind osmosis is the concentration gradient of the solute. Water tends to move toward areas with a higher concentration of solutes in order to dilute them and achieve an equilibrium in concentration. This process is vital for maintaining proper hydration and nutrient balance within cells and organisms.
The movement of water across the membrane occurs through specialized channels called aquaporins, though it can also move directly through the membrane. Osmosis doesn’t require energy input, making it a passive process.
In a biological system, the direction of water movement depends on the relative concentrations of solute inside and outside of a cell. If a cell is placed in a solution with a higher concentration of solute (hypertonic solution), water will move out of the cell, causing it to shrink. If the cell is in a solution with a lower concentration of solute (hypotonic solution), water will move into the cell, causing it to swell. In an isotonic solution, where the solute concentrations are equal inside and outside of the cell, there will be no net movement of water.
Osmosis is essential for maintaining cell function and balance in organisms. It plays a key role in processes like nutrient absorption in the intestines, water regulation in kidneys, and the exchange of gases in plant roots.