AP BIOLOGY

Detailed explanation-1: -This is a type of passive transport in which molecules that cross the cell membrane move quickly due to the presence of specific permeases in the membrane. Facilitated diffusion occurs only in the direction of a concentration gradient and does not require metabolic energy.

Detailed explanation-2: -Passive transport occurs when substances cross the plasma membrane without any input of energy from the cell. No energy is needed because the substances are moving from an area where they have a higher concentration to an area where they have a lower concentration. Water solutions are very important in biology.

Detailed explanation-3: -Not everything enters the cell through passive transport. Only the smallest molecules like water, carbon dioxide, and oxygen can freely diffuse across cell membranes. Larger molecules or charged molecules often require an input of energy to be transported into the cell.

Detailed explanation-4: -No energy is needed from the cell for passive transport because it occurs when substances move naturally from an area of higher concentration to an area of lower concentration. Simple diffusion is the movement of a substance due to differences in concentration. It happens without any help from other molecules.

Detailed explanation-5: -Active transport requires energy for the movement of molecules whereas passive transport does not require energy for the movement of molecules. In active transport, the molecules move against the concentration gradient whereas in passive transport, the molecules move along the concentration gradient.