A semipermeable membrane is made from _______, with small ____ or _______. These are too large to pass through a semipermeable membrane.

A semipermeable membrane is made from _______, with small ____ or _______. These are too large to pass through a semipermeable membrane.

• A. Carbohydrates; bacteria and viruses
• B. Protein; red blood cells and proteins
• C. Lipids; ions and molecules
• D. Nucleic acids; salts

Answer: (B)

Selective permeability is what this item tests: a semipermeable membrane acts as a barrier that allows only certain things to pass based on size and the presence of channels. The membrane is built from protein, which forms pores or channels that regulate what can move through. Because of these openings, very large particles—like red blood cells and many proteins—are too big to fit through, so they cannot cross the membrane. In contrast, small solutes can pass through the channels or rely on the lipid bilayer for diffusion, depending on their size and properties. The other options describe components or examples that don’t align with this size-based selectivity: the building material isn’t primarily lipids or nucleic acids in the context of this statement, and the blocked items aren’t simply ions or salts.

Selective permeability is what this item tests: a semipermeable membrane acts as a barrier that allows only certain things to pass based on size and the presence of channels. The membrane is built from protein, which forms pores or channels that regulate what can move through. Because of these openings, very large particles—like red blood cells and many proteins—are too big to fit through, so they cannot cross the membrane. In contrast, small solutes can pass through the channels or rely on the lipid bilayer for diffusion, depending on their size and properties. The other options describe components or examples that don’t align with this size-based selectivity: the building material isn’t primarily lipids or nucleic acids in the context of this statement, and the blocked items aren’t simply ions or salts.