Final answer:
A semipermeable membrane in osmosis serves to selectively allow water molecules to pass through while blocking larger solutes, enabling the equalization of solute concentrations on both sides of the membrane.
Step-by-step explanation:
The main function of a semipermeable membrane in osmosis is to allow the passage of water molecules while restricting the movement of certain solutes (like salts, sugars, proteins).
This selective permeability is essential for maintaining the balance of concentrations on either side of the membrane.
During osmosis, water moves from an area of higher water concentration through the semipermeable membrane to an area of lower water concentration.
The water flows until the solute concentrations on both sides of the membrane are more balanced, eventually reaching an equilibrium.
Osmosis, crucial in biological systems, is facilitated by aquaporins and other mechanisms within the cell membrane. This process affects various physiological functions, such as nutrient absorption and waste removal in cells, and helps maintain the proper internal environment in organisms.