AP BIOLOGY

Detailed explanation-1: -Passive transport: This does not require any energy expenditure as it occurs along the concentration gradient of the molecule being translocated.

Detailed explanation-2: -Facilitated diffusion. Some molecules, such as carbon dioxide and oxygen, can diffuse across the plasma membrane directly, but others need help to cross its hydrophobic core. In facilitated diffusion, molecules diffuse across the plasma membrane with assistance from membrane proteins, such as channels and carriers.

Detailed explanation-3: -area with lower concentration. The difference between the concentrations is called the “concentration gradient”. Diffusion goes down the gradient until an equilibrium is reached.

Detailed explanation-4: -Neutral solutes can move across the plasma membrane along the concentration gradient by the process of simple diffusion. As the solutes move along the concentration gradient, a carrier is not required.