Question

Materials like oxygen and carbon dioxide enter and leave cells by diffusion.

• A. Diffusion
• B. Active transport
• C. Passive transport
• D. Osmosis

Answer 1

The correct option is A Diffusion

Materials like oxygen, carbon dioxide enter and leave cells by diffusion. When a cell is respiring the concentration of oxygen inside the cell is lower than the surrounding blood so it moves into the cell. As carbon dioxide is produced the concentration inside the cell increases to a level higher than the surrounding blood, so carbon dioxide diffuses out of the cell. Cell membranes are very thin to allow materials to diffuse through them easily.
Example: the movement of carbon dioxide and oxygen in the lungs and in leaves.