How does particle size affect a molecule's ability to move across a cell membrane?

• A. Smaller particles are unable to move across the membrane due to their size.
• B. Smaller particles move more easily across the membrane due to less resistance.
• C. Particle size does not affect movement across the membrane; only concentration matters.
• D. Larger particles move more easily across the membrane due to greater kinetic energy.

Answer: (B)

Verified step by step guidance

1. Understand the structure of the cell membrane: The cell membrane is primarily composed of a phospholipid bilayer with embedded proteins, which creates a semi-permeable barrier.
2. Consider the concept of diffusion: Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. Smaller particles generally diffuse more easily due to less resistance.
3. Analyze the role of particle size: Smaller particles can move more easily across the cell membrane because they encounter less resistance and can pass through the small spaces between the phospholipids.
4. Evaluate the impact of kinetic energy: While larger particles may have greater kinetic energy, their size can hinder their ability to pass through the membrane compared to smaller particles.
5. Conclude with the correct understanding: Smaller particles move more easily across the membrane due to less resistance, aligning with the principles of diffusion and membrane permeability.