Facilitated Diffusion

Which of the following best defines a concentration gradient?

• The uniform distribution of molecules across a space.

• The difference in the concentration of molecules across two regions, typically across a membrane.

• The movement of molecules from a lower concentration to a higher concentration.

• The process by which molecules are evenly distributed in a solution.

Which of the following is most likely to be transported by facilitated diffusion?

• Oxygen molecules

• Small nonpolar molecules

• Highly charged ions like sodium ions (Na+)

• Water molecules

Channel-mediated diffusion is most associated with the movement of:

• Large molecules like glucose

• Small, nonpolar molecules

• Water through aquaporins

• Highly charged ions through specific ion channels

In facilitated diffusion, which type of transport protein is used to move large or charged molecules across the membrane?

• Carrier proteins

• Ion channels

• Enzymes

• Receptor proteins

Which of the following is true about the movement of sodium ions (Na+) during facilitated diffusion?

• They move through carrier proteins against their concentration gradient.

• They are transported by osmosis.

• They enter the cell through active transport mechanisms.

• They require ion channels to move down their concentration gradient.

Which of the following statements best describes gated channel proteins?

• They facilitate the movement of water molecules across the membrane.

• They actively pump ions across the membrane using ATP.

• They open or close in response to specific stimuli, allowing the selective passage of ions or molecules.

• They are always open and allow any molecule to pass through the membrane.

Which of the following molecules is transported into cells via carrier-mediated facilitated diffusion?

• Glucose

• Oxygen

• Water

• Sodium ions

Carrier-mediated diffusion is different from channel-mediated diffusion because:

• Carrier-mediated diffusion requires energy.

• Channel proteins are more specific in their function.

• Carrier proteins change shape to move molecules across the membrane.

• Channel-mediated diffusion only moves water molecules.

Which of the following statements best describes facilitated diffusion?

• Movement of molecules against their concentration gradient using energy.

• Passive movement of water across a semipermeable membrane.

• Active transport of ions using ATP.

• Movement of molecules down their concentration gradient without the use of energy but requiring transport proteins.

Which of the following describes what happens to molecules during facilitated diffusion until equilibrium is reached?

• Molecules move in one direction only, from high to low concentration, and stop once equilibrium is achieved.

• Molecules move randomly, and their movement stops as soon as the concentration is equal on both sides of the membrane.

• Molecules continue to move back and forth across the membrane, but there is no net movement once the concentration is equal on both sides.

• Molecules are actively transported until the concentrations are equal.