2.1.3 Osmosis, diffusion and membrane transport Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 2

The 20 questions

1. What is osmosis?

   • The net movement of water molecules across a partially permeable membrane from a dilute solution to a more concentrated solution
   • The movement of large molecules in bulk across the membrane inside vesicles
   • The active movement of water against its concentration gradient using energy released from ATP
   • The net movement of solute molecules across a partially permeable membrane from a concentrated solution to a dilute one

2. Which of these is passive transport?

   • Exocytosis of digestive enzymes from a secretory cell
   • Active uptake of glucose against a concentration gradient using ATP
   • Simple diffusion of oxygen across the cell membrane
   • Endocytosis of a large protein molecule into a vesicle

3. Which process uses ATP directly to move substances against a concentration gradient?

   • Facilitated diffusion
   • Osmosis
   • Simple diffusion
   • Active transport

4. What is the role of ATP in active transport?

   • It is the substance that is transported across the membrane by the carrier protein
   • It provides immediate energy, for example by phosphorylating a carrier protein to change its shape
   • It acts as the carrier protein that binds substances and moves them across the membrane
   • It forms a channel that allows water to pass through the membrane by osmosis

5. Which of these describes facilitated diffusion?

   • Movement of a substance in bulk inside a vesicle that fuses with the membrane
   • Diffusion of a substance down its concentration gradient through a channel or carrier protein
   • Movement of water through a membrane from a concentrated to a dilute solution by osmosis
   • Diffusion of a substance against its concentration gradient using energy from ATP

6. What is the function of a channel protein in membrane transport?

   • It forms the hydrophobic core of the membrane through which all molecules must pass
   • It provides a water-filled pore through which specific ions or small polar molecules can diffuse
   • It binds a solute and changes shape to move it against its concentration gradient using ATP
   • It digests large molecules into smaller units before they enter the cell

7. What happens to a plant cell placed in a solution with a lower water potential than the cell?

   • No water moves, because the solution does not affect the water in the cell
   • Water enters the cell by osmosis, and the cell becomes turgid and bursts
   • Water leaves the cell by osmosis, and the cell becomes flaccid or plasmolysed
   • Solutes leave the cell by active transport, which stops water movement entirely

8. Which process moves large molecules such as proteins into a cell in vesicles?

   • Simple diffusion
   • Osmosis
   • Exocytosis
   • Endocytosis

9. A potato cylinder is placed in a sucrose solution and its mass increases by 10%. What is the most likely explanation?

   • The cylinder absorbed sucrose by active transport, which increased its dry mass
   • Water left the cells by osmosis, because the solution had a lower water potential than the cells
   • Water entered the cells by osmosis because the solution had a higher water potential than the cells
   • Sucrose entered the cells by osmosis, because sucrose is a partially permeable substance

10. Which factor increases the rate of simple diffusion across a membrane?

    • An increase in the thickness of the membrane
    • A decrease in the temperature of the surroundings
    • A steeper concentration gradient across the membrane
    • A decrease in the surface area of the membrane

11. Why is facilitated diffusion faster than simple diffusion for a polar molecule such as glucose?

    • Glucose is non-polar, so it passes freely through the bilayer by simple diffusion
    • The membrane becomes thinner in the presence of glucose, which speeds diffusion
    • A carrier protein moves the glucose against its concentration gradient using energy from ATP
    • A carrier protein provides a route across a membrane that the hydrophobic core would otherwise block

12. Which of these is a feature of active transport?

    • It always moves substances in bulk using vesicles
    • It requires no energy and moves substances down a concentration gradient
    • It requires energy from ATP and involves carrier proteins
    • It involves water moving across a partially permeable membrane only

13. Why do cells need active transport for the uptake of ions such as sodium and potassium?

    • The ions can pass only through the bilayer when ATP is present to dissolve the lipids
    • The ions must sometimes be moved against their concentration gradients, which requires energy
    • The ions are too large to pass through the membrane by any process, so energy is needed to break them down
    • The ions are always moved down their gradients, which requires energy to stop them diffusing

14. Which of these is most likely to cause a red blood cell to lose water by osmosis?

    • Placing it in a dilute salt solution with a higher water potential than the cell
    • Placing it in pure water, which has the highest water potential
    • Placing it in a concentrated salt solution with a lower water potential than the cell
    • Placing it in an isotonic solution, which has the same water potential as the cell

15. Which statement about exocytosis is correct?

    • It moves ions across the membrane through channel proteins, which are open at all times
    • It moves substances out of the cell in vesicles that fuse with the membrane, and it uses energy
    • It moves substances into the cell in vesicles, and it requires no energy from the cell
    • It moves water out of the cell by osmosis, and it is driven by the concentration gradient

16. Which of these explains why a partially permeable membrane allows water to pass through but blocks some solutes?

    • Water molecules are small enough to pass through, but larger solute molecules cannot pass the pores
    • Water molecules are large and charged, so they can move only through specific channel proteins
    • Solutes are small and non-polar, so they pass easily while water is blocked by the hydrophobic core
    • Water and solutes both pass through the membrane at the same rate, so the membrane is not selective

17. Which of these describes the difference between simple diffusion and osmosis?

    • Simple diffusion moves any molecule down a gradient, whereas osmosis specifically moves water across a partially permeable membrane
    • Simple diffusion moves only water across a membrane, whereas osmosis moves any molecule down a concentration gradient across a membrane
    • Osmosis moves solutes against a concentration gradient using carrier proteins, whereas simple diffusion moves water with the gradient
    • Simple diffusion requires ATP from respiration to move molecules, whereas osmosis is a passive process that uses no energy at all

18. A student predicts the change in mass of a potato cylinder placed in a solution of higher water potential than the cell contents. Which prediction is correct?

    • The cylinder is unchanged in mass, because osmosis does not occur in plant tissues
    • The cylinder loses mass, because solutes leave the cells by active transport
    • The cylinder loses mass, because water leaves the cells by osmosis
    • The cylinder gains mass, because water enters the cells by osmosis

19. A visking tube containing starch solution is placed in water. Iodine solution is then added to the water outside the tube and the water stays orange-brown. What does this show?

    • Iodine was actively transported into the tube, using ATP released from the starch solution
    • Starch diffused out of the tube, so the membrane is fully permeable to starch molecules
    • Starch did not diffuse out of the tube, so the membrane is impermeable to starch
    • Water passed into the tube, which turned the starch solution orange-brown inside the tube

20. Which process takes in a large volume of fluid and dissolved solutes into a cell in bulk?

    • Active transport, which moves fluid against a gradient using ATP and carrier proteins alone
    • Osmosis, which moves water down a gradient only into the cytoplasm of the cell
    • Facilitated diffusion, which moves fluid through carrier proteins down a gradient
    • Endocytosis, which engulfs fluid and solutes in vesicles formed from the membrane

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