AP BIOLOGY

Detailed explanation-1: -Passive transport occurs by simple diffusion or via pores in the plasma membrane (Figure 3.2).

Detailed explanation-2: -The simplest mechanism by which molecules can cross the plasma membrane is passive diffusion. During passive diffusion, a molecule simply dissolves in the phospholipid bilayer, diffuses across it, and then dissolves in the aqueous solution at the other side of the membrane.

Detailed explanation-3: -The simplest forms of transport across a membrane are passive. Passive transport does not require the cell to expend any energy and involves a substance diffusing down its concentration gradient across a membrane.

Detailed explanation-4: -Simple diffusion and osmosis are both forms of passive transport and require none of the cell’s ATP energy.