AP BIOLOGY

Detailed explanation-1: -In facilitated diffusion, substances move into or out of cells down their concentration gradient through protein channels in the cell membrane. Simple diffusion and facilitated diffusion are similar in that both involve movement down the concentration gradient.

Detailed explanation-2: -Oxygen is diffusing from the air inside the alveoli within the lungs into the erythrocytes and blood plasma. Diffusion is a type of passive transport, where molecules move from high concentration to low concentration.

Detailed explanation-3: -Oxygen moves down a concentration gradient from the air in the alveoli to the blood. Carbon dioxide moves down a concentration gradient from the blood to the air in the alveoli.

Detailed explanation-4: -Oxygen diffuses through the cell membrane and is transported in blood plasma by free diffusion and by convection.

Detailed explanation-5: -Passive transport describes the movement of substances down a concentration gradient and does not require energy consumption. Diffusion is the net movement of substances from an area of higher concentration to an area of lower concentration.