Question

passive transport occurs when molecules cross the cell membrane without using cellular energy. molecules cross the cell membrane by three main types of passive transport: simple diffusion, facilitated diffusion, and osmosis.
select the true statements.
simple diffusion moves molecules from areas of higher to lower concentration, while facilitated diffusion moves molecules from areas of lower to higher concentration.
as molecules move randomly, they collide with each other and spread out down their concentration gradients.
energy from the cell is required to move molecules from areas of higher concentration to areas of lower concentration.
all molecules are able to cross the cell membrane by osmosis.

Explanation:

• Simple diffusion and facilitated diffusion both move molecules from higher to lower concentration. So the first statement is false.
• Molecules in passive transport move randomly, collide, and spread down concentration gradients. This makes the second statement true.
• Passive transport (including movement from higher to lower concentration) does not require cell energy. So the third statement is false.
• Osmosis is specifically for water molecules. Not all molecules can cross by osmosis. So the fourth statement is false.

Answer:

Only the statement “As molecules move randomly, they collide with each other and spread out down their concentration gradients.” is true.