Author: Biology Junction Team

Cellular Transport Review: Apply, Explain, and Revise

Cells and Transport Teaching Resources · High school biology; AP extensions where noted.

Use this cumulative review after membrane structure and osmosis lessons. Students should explain the mechanism and assumptions in each response, then revise with feedback. Materials: notebook, pencil, and optional copy of the existing Word review.

Learning objectives

  • Choose a transport mechanism using evidence about molecules, gradients, and energy.
  • Interpret tonicity without treating water as stationary at equilibrium.
  • Use a simple data set to evaluate a claim.

Original review tasks

  1. An oxygen molecule crosses the lipid portion of a membrane toward a region with lower oxygen concentration. Name the mechanism and explain whether direct ATP input is needed.
  2. A carrier transports glucose down its concentration gradient without energy coupling. Explain why “a protein is involved” does not make this active transport.
  3. A cell exports a packaged digestive enzyme. Describe the membrane event rather than say the protein diffuses out.
  4. A model cell contains nonpenetrating solute and is water-permeable. It loses volume in a test solution at initially equal pressure. What does this suggest about the solution’s tonicity relative to that cell?
  5. Three eggs in one treatment change mass by +6%, +8%, and +10%. Calculate the mean and range. Does this establish that all cell membranes behave identically?
  6. A student writes, “Active transport always uses ATP directly at the transporter.” Improve the statement by distinguishing primary from secondary active transport.
  7. Explain one way a plant wall changes the consequences of water entry without replacing the plasma membrane.
  8. Draw water movement across an isotonic animal-cell membrane, then explain how the drawing represents constant average cell volume.

Feedback on the original tasks

  1. Simple diffusion; the described downhill crossing does not use ATP directly.
  2. Facilitated diffusion is passive. Classify using gradient and energy coupling, not the presence of a protein alone.
  3. A vesicle fuses with the plasma membrane and releases its contents by exocytosis.
  4. The surroundings are consistent with a hypertonic solution under the stated assumptions. Check permeability and cell integrity before generalizing.
  5. The mean is +8%; the range spans +6% to +10% (a 4-percentage-point spread). Egg membranes are a limited model and this small data set cannot establish a universal rule.
  6. Primary transport uses energy directly; secondary transport couples one substance’s uphill movement to another’s downhill electrochemical movement.
  7. The wall resists expansion and permits turgor pressure to build. The membrane still regulates exchange.
  8. Show movement both ways with balanced rates; volume stability does not imply stationary water.

Existing Word review

Download the legacy Cellular Transport Review (Word .doc). It includes tonicity prompts, multiple choice, term completion, diagram questions, and a transport comparison table. The file credits a Brookings school resource. Check permissions and diagram layout before distributing an adapted copy. The feedback above applies only to the new on-page tasks.

Teacher notes on the legacy review

Several items simplify biology too far: glucose entry depends on the cell and transporter; mitochondria are not every cell’s only ATP source; and turgor pressure is not interchangeable with osmotic pressure. Review those items before grading. Do not infer answers to a missing diagram from the surrounding text.

Use incorrect responses to assign a focused next task: membrane structure, gradient reasoning, or interpretation of data. For AP, ask students to describe the electrical information needed for an ion-transport prediction.

Continue the unit

Sources and further reading