Question

complete the table to compare the three types of passive transport.
simple diffusion: molecules cross the membrane through the phospholipids, molecules cross the membrane through proteins, molecules move down their concentration gradient, molecules move without using cellular energy
facilitated diffusion
osmosis

Explanation:

Step1: Recall simple diffusion

Simple diffusion is a passive process where small, non - polar molecules move from an area of high concentration to an area of low concentration directly through the phospholipid bilayer of the cell membrane without the use of energy or proteins.

Step2: Recall facilitated diffusion

Facilitated diffusion is also passive, so no energy is used. Molecules move down their concentration gradient, but they require transport proteins (carrier or channel proteins) to cross the membrane as they are either large or polar.

Step3: Recall osmosis

Osmosis is the diffusion of water across a semi - permeable membrane. It is a passive process, so no energy is consumed. Water moves down its concentration gradient. While water can move through the lipid bilayer to some extent, aquaporin proteins can also facilitate the movement of water, but the main pathway of water movement is still considered to be through the phospholipid bilayer in the context of the lipid - based membrane structure.

Answer:

Transport Type	Energy Requirement	Movement Down Concentration Gradient	Membrane - crossing via Proteins	Membrane - crossing via Phospholipids
Facilitated Diffusion	No	Yes	Yes	No
Osmosis	No	Yes (for water)	No (water channels may be involved but not in the same sense as protein - mediated for solutes)	Yes (water moves through the lipid bilayer or aquaporins)