Which type(s) of molecules cannot enter/exit the cell via simple diffusion and require facilitated diffusion?

• A. Nonpolar oxygen gas molecules.
• B. Charged Ca²⁺ ions
• C. Nonpolar carbon dioxide gas molecules.
• D. Nonpolar water molecules
• E. Charged Na⁺ ions
• F. b and e only
• G. a, c, and d only

Answer: (F)

Verified step by step guidance

1. Understand the concept of simple diffusion: Simple diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration without the need for energy or assistance from proteins. It typically involves small, nonpolar molecules.
2. Identify the characteristics of molecules that use facilitated diffusion: Facilitated diffusion is used by molecules that cannot easily pass through the lipid bilayer due to their size, polarity, or charge. These molecules require the help of transport proteins.
3. Analyze the given molecules: Nonpolar molecules like oxygen (O2) and carbon dioxide (CO2) can pass through the cell membrane via simple diffusion because they are small and nonpolar. Water, although polar, can also diffuse through the membrane due to its small size, but it can also use aquaporins for facilitated diffusion.
4. Focus on charged ions: Charged ions like Ca2+ and Na+ cannot pass through the hydrophobic lipid bilayer via simple diffusion due to their charge. They require ion channels or transport proteins for facilitated diffusion.
5. Conclude which molecules require facilitated diffusion: Based on the analysis, charged ions such as Ca2+ and Na+ require facilitated diffusion, while nonpolar molecules like oxygen, carbon dioxide, and water can use simple diffusion.