All cells are surrounded by a semipermeable membrane, which regulates the passage of materials in and out of the cell. the principle structure of this membrane is
a. two layers of protein with a single layer of lipids in between.
b. a thick wall of cellulose with a thin lipid coating on the inside.
c. two layers of lipids with proteins associated with the lipids.
d. two layers of lipids with a polysaccharide layer in between.

The blue particles in this image are able to cross the cell membrane through simple diffusion. how will they be transported? outside the cell inside the cell o a. the substances will move directly across the membrane from outside the cell to inside the cell. b. the substances will move through channels in the membrane proteins from outside the cell to inside the cell. o c. the substances will move through channels in the membrane proteins from inside the cell to outside the cell. o d. the substances will move directly across the membrane from inside the cell to outside the cell.