Question

Cell membranes are said to be selectively permeable. Which statement best explains what selectively permeable means? *a. The cell membrane prevents any harmful substance from entering the cell.b. The cell membrane lets certain substances enter the cell and keeps certain substances out of the cell.c. The cell membrane allows only large molecules to diffuse into the cell.d. The cell membrane has pores that let only water and glucose into the cell and carbon dioxide out.e. I don't know and would rather not guess

Answer 1

Well, we have to consider that selective permeability gives the cell the capacity of selecting what enters, and what exits from the extracellular media, and from the cytoplasm. So beyond avoiding toxic or harmful substances to get in, the cell membrane lets certain substances enter and get out of the cell, like carbohydrates, CO2, and other molecules, like water.

Having this in mind, we could say that the answer is the b option.

B. The cell membrane lets certain substances enter the cell and keeps certain substances out of the cell.