Which term describes a property of cell membranes that allows some substances to pass through, while others cannot?

Which term describes a property of cell membranes that allows some substances to pass through, while others cannot?

• A. Selectively permeable membrane
• B. Isotonic solution
• C. Osmosis
• D. Diffusion

Answer: (A)

Selective permeability is the property of a cell membrane that lets some substances pass through while others cannot. The membrane’s phospholipid bilayer, along with embedded transport proteins, creates gated routes that differentiate by size, charge, and polarity. Small nonpolar molecules can pass through the lipid bilayer, while ions and larger polar molecules need channels or carriers to cross. This selective gatekeeping lets the cell take in nutrients, expel wastes, and maintain a stable internal environment. The other terms describe processes or conditions rather than the membrane’s ability to regulate passage: isotonic refers to equal solute concentrations between two solutions, osmosis is water movement across a membrane toward higher solute concentration, and diffusion is the general idea of particles moving from high to low concentration, which can occur with or without membrane proteins but doesn’t define the membrane’s selective barrier.

Selective permeability is the property of a cell membrane that lets some substances pass through while others cannot. The membrane’s phospholipid bilayer, along with embedded transport proteins, creates gated routes that differentiate by size, charge, and polarity. Small nonpolar molecules can pass through the lipid bilayer, while ions and larger polar molecules need channels or carriers to cross. This selective gatekeeping lets the cell take in nutrients, expel wastes, and maintain a stable internal environment. The other terms describe processes or conditions rather than the membrane’s ability to regulate passage: isotonic refers to equal solute concentrations between two solutions, osmosis is water movement across a membrane toward higher solute concentration, and diffusion is the general idea of particles moving from high to low concentration, which can occur with or without membrane proteins but doesn’t define the membrane’s selective barrier.