Cell Membrane Control Practice Test

A cell model shows a visible boundary labeled cell membrane. The inside is shaded gray and the outside is white. Two substances are shown outside: “salt (NaCl)” with an arrow that crosses into the cell, and “plastic bead (P)” with an arrow that stops at the boundary (does not cross). The model states: “The membrane regulates exchange.”

Which substance can enter the cell based on the model, and what does that show about membrane control?

A model shows a cell with a boundary labeled cell membrane. Inside and outside are labeled. Arrows show water entering and waste leaving. A “paint drop” symbol is shown outside with a blocked mark (⛔) at the boundary. The model states: “The membrane regulates what enters and leaves the cell.”

A student says: “The membrane is just the edge of the cell. It does not control anything; substances cross whenever they touch it.” Which choice best evaluates the student’s claim using the model?