Name: ______Date: ______Period: ______

5.16 Osmosis and Cell Transport

  • Cells need to maintain homeostasis (balance). One of the ways they do this is regulating what comes in and out of the cell (the plasma/cell membrane is in charge of this!)
  • The cell membrane is semi permeable: it lets some stuff through but not everything
  • Cell transport is moving stuff across the cell membrane
  • Active Transport: This requires energy (ATP) because you are going from a LOW concentration to a HIGH concentration (think about going UP a hill)
  • Passive Transport: Does not require energy (ATP) because you are going from HIGH to LOW concentration (think about going DOWN a hill)
  • Diffusion: HIGH to LOW
  • Facilitated Diffusion: HIGH to LOW with a helper protein
  • Osmosis: Diffusion of water
  • A solution has two parts:
  • Solute: what is being dissolved (usually salt or sugar—glucose, starch, etc)
  • Solvent: the liquid doing the dissolving (usually water)
  • Osmosis the movement of water is when the solute is too large to pass through the membrane, so the water moves.
  • Water always goes to the party (party = where more solute—salt or sugar—is!)
  • Hypotonic Solution: A solution that has LESS solute than the other solution
  • Hippo
  • Water moves AWAY from the hypotonic solution
  • Hypertonic Solution: A solution that has MORE solute than the other solution
  • Water moves TOWARD the hypertonic solution (it has the party!)
  • Isotonic solution: Same concentration of solute on BOTH sides of the membrane

Hypotonic Solution / Isotonic Solution / Hypertonic Solution
Animal Cell / / /
Plant Cell / / /
  1. Zucchini cores placed in sucrose solutions resulted in the following percent changes after 24 hours.

Sucrose Concentration / % Change in Mass
0.0 M (distilled water) / 16%
0.2 M / 8%
0.4 M / -7%
0.6 M / -17%
0.8 M / -25%
1.0 M / -30%
  1. In 0.2M, does the core increase in mass or decrease in mass? ______
  2. In 0.2M, did the core gain water or lose water? ______
  3. In 0.4M, does the core increase in mass or decrease in mass? ______
  4. In 0.4M, did the core gain water or lose water? ______
  5. When the cell and environment are isotonic (equal concentrations), the cell does not gain water, and the cell does not lose water. There would be no change. Based on this observation, if a cell was placed in an isotonic solution, what would be the % change in mass? ______%
  6. At what point is the zucchini isotonic to the sucrose solution? _____M
  7. How do you know?

______

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2. Osmosis is the diffusion of ______across a membrane, from a high concentration to a low concentration

A. Molecules

B. Water

C. Cytoplasm

D. Chromosomes

3. Which transport requires energy (ATP)?

A. Passive

B. Diffusion

C. Active

D. Osmosis

4. In this type of solution there is an even exchange of water going into the cell and leaving the cell.

A. Hypotonic

B. Hypertonic

C. Isotonic

D. Equilibrium

5. A freshwater plant is placed in a container of saltwater. What will most likely happen to the cells of the plant?

  1. They will swell because water will move into them.
  2. They will swell because salt will move into them.
  3. They will swell because both water and salt will move into them.
  4. They will shrink because salt will move out of them.
  5. They will shrink because water will move out of them.
  1. Let’s say we place a potato cell into a solution with a lower salt concentration.
  2. Does the potato have the higher or lower salt concentration compared to the solution? ______
  3. Water follows the salt! Where would the water go? Would it leave the potato cell or enter the potato cell? ______

7. In this experiment, water enters and leaves the plant cells primarily by

  1. Facilitated diffusion
  2. Active transport
  3. Endocytosis
  4. Phagocytosis
  5. Osmosis

8. What is the approximate concentration that would represent an isotonic solution?

A. 0.0 M

B. 0.1 M

C. 0.3 M

D. 0.5 M

E. 0.8 M

9. What would be expected to happen if a plant cell were placed in a hypotonic solution?

  1. Water will enter the cell, causing it to swell and bust
  2. Water will leave the cell, causing it to shrink.
  3. Water will enter the cell, causing it to swell and become turgid.
  4. Water will leave the cell, causing glucose to leave the cell as well.
  5. Water will move equally in both directions, causing the cell to remain the same.

10. In this type of solution there is a high concentration of molecules inside of the cell than in the solution/environment.

A. Hypotonic

B. Hypertonic

C. Isotonic

D. Equilibrium

11. Which of the following best describes an organism’s attempt to maintain cellular homeostasis?

  1. A flowing plant bends toward a light source
  2. A paramecium’s contractile vacuole expels excess water from the cell
  3. A small bird lays three eggs in its nest
  4. A puppy growls when another puppy tries to take its bone
  5. An earthworm’s DNA is replicated

12.. Make a claim on the level of permeability of the cell membrane below. Provide evidence and justify.

Possible sentence starters, and by no means the best.

C: “The cell is…” (State what it is and END the sentence.)

E: “Per the diagram, …”

R: “I know that…”

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