Biological membranes are indeed selectively permeable membranes. This means that they allow some substances to pass through while blocking others based on their size, charge, and solubility. Here's why this statement is true:
1. Composition of Biological Membranes: Biological membranes, such as cell membranes, are composed of a lipid bilayer embedded with proteins. This lipid bilayer serves as a barrier to the free movement of substances.
2. Selective Permeability: The lipid bilayer is selectively permeable because of its structure. Small, non-polar molecules like oxygen and carbon dioxide can pass through easily due to their ability to dissolve in the lipid layer. On the other hand, larger molecules, ions, and polar molecules may require specific channels or transport proteins to cross the membrane.
3. Examples of Selective Permeability: For instance, water molecules can pass through cell membranes via specialized channels called aquaporins, which facilitate their movement. Similarly, glucose requires transporter proteins to cross the membrane because it is polar and cannot diffuse through the lipid bilayer.
In conclusion, the statement that biological membranes are selectively permeable is true, as they regulate the passage of substances into and out of cells based on specific criteria, ensuring proper cellular function and maintaining homeostasis.
