Final answer:
Simple diffusion and facilitated diffusion are both forms of passive transport that move substances down their concentration gradient. In simple diffusion, particles or solutes flow freely through the lipid bilayer of the plasma membrane. In facilitated diffusion, particles or solutes require assistance from transport proteins to move across the membrane.
Step-by-step explanation:
Simple diffusion and facilitated diffusion are both forms of passive transport that move substances down their concentration gradient. In simple diffusion, substances move directly through the lipid bilayer of the plasma membrane, while in facilitated diffusion, substances move through specific transport proteins embedded in the membrane.
In simple diffusion, particles or solutes flow freely from an area of higher concentration to an area of lower concentration. This process does not require any energy and only depends on the solute's ability to pass through the lipid bilayer. Examples of substances that can undergo simple diffusion include oxygen and carbon dioxide.
On the other hand, in facilitated diffusion, particles or solutes require assistance from transport proteins to move across the plasma membrane. These transport proteins act as channels or carriers that allow specific molecules or ions to pass through. Facilitated diffusion is still considered passive transport because it does not require energy and the solute is moving down its concentration gradient. Glucose and certain ions, such as sodium ions, are examples of substances that undergo facilitated diffusion.