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 of the cell membrane. These are usually polar or charged molecules that require the help of transport proteins.
3. Analyze the given molecules: Nonpolar molecules like oxygen gas (O2) and carbon dioxide (CO2) can pass through the cell membrane via simple diffusion due to their nonpolar nature. Water molecules, although polar, can also pass through the membrane to some extent due to their small size.
4. Focus on charged ions: Charged ions such as Ca2+ and Na+ cannot pass through the lipid bilayer via simple diffusion because the hydrophobic core of the membrane repels charged particles. These ions require facilitated diffusion, which involves specific transport proteins or channels.
5. Conclude which molecules require facilitated diffusion: Based on the analysis, charged ions like Ca2+ and Na+ require facilitated diffusion to enter or exit the cell, while nonpolar molecules like oxygen, carbon dioxide, and water can use simple diffusion.