Question

how does osmosis differ from simple diffusion?
a. osmosis requires energy input.
b. osmosis specifically involves the movement of water molecules.
c. osmosis involves the movement of proteins across the membrane.
d. osmosis occurs against a concentration gradient.
which molecules can pass through the phospholipid bilayer via simple diffusion?
a. small nonpolar molecules like oxygen and carbon dioxide
b. ions like sodium and potassium
c. proteins
d. large polar molecules like glucose

Explanation:

• Osmosis is the movement of water molecules across a semi - permeable membrane from an area of lower solute concentration to an area of higher solute concentration. Simple diffusion is the movement of molecules (not just water) from an area of higher concentration to an area of lower concentration. So, osmosis specifically involves water molecules.
• Small non - polar molecules like oxygen and carbon dioxide can pass through the phospholipid bilayer via simple diffusion because the non - polar tails of the phospholipids allow non - polar molecules to pass through easily. Ions (like sodium and potassium) and large polar molecules (like glucose) and proteins cannot pass through easily via simple diffusion as the phospholipid bilayer is not permeable to them (ions and large polar molecules are polar, and proteins are large).

Answer:

• First question: B. Osmosis specifically involves the movement of water molecules.
• Second question: A. Small nonpolar molecules like oxygen and carbon dioxide.