FranksBio.net

Unit 4

BIO.1D - Cell Transport

Unit 4: Need to Know and Be Able to Do

BIO.1D.1 - Proving the Membrane Is Semipermeable

Need to know

  • Semipermeable means some substances can cross a membrane while others cannot.
  • Whether a substance crosses depends on particle size compared with pore size.
  • Passive transport moves substances with the concentration gradient and does not require energy.
  • Active transport moves substances against the concentration gradient and requires ATP.
  • The concentration gradient is the difference in concentration between two areas.
  • The sodium-potassium pump is active transport: it moves 3 Na+ out and 2 K+ in, against the gradient, using ATP.
  • Both active and passive transport help a cell maintain homeostasis.

Be able to do

  • Design a permeability investigation by varying salt concentration across several cups and measuring mass change in potato slices.
  • Complete missing procedural steps, including setting up the independent variable and taking measurements.
  • Predict that only water, not large sugar molecules, crosses a semipermeable membrane in an appropriate model.
  • Interpret dialysis tubing and starch models as representations of a cell membrane.

Watch out for

  • Mass change is the evidence. State what gained or lost mass and explain why.
  • Movement with the concentration gradient is passive; movement against it requires active transport and ATP.

BIO.1D.2 - Solute Imbalance and Osmosis

Need to know

  • Osmosis is the movement of water across a semipermeable membrane.
  • Water moves toward the higher solute concentration.
  • When the outside is hypertonic, water leaves the cell. When the outside is hypotonic, water enters. In an isotonic solution, there is no net movement.
  • The sodium-potassium pump moves 3 Na+ out and 2 K+ in using energy.

Be able to do

  • Predict the direction of water movement by comparing solute concentrations inside and outside a cell.
  • Label a solution hypertonic, hypotonic, or isotonic from mass-change data.
  • Predict whether a plant cell becomes firm or limp from tonicity data.
  • Interpret a dialysis-pouch model by comparing the two solute concentrations.

Watch out for

  • When water crosses the membrane, the process is osmosis, not diffusion.
  • Water moves toward the solute. Remember: water follows solute.
Unit 4 Flashcards

Study the essential terms for cell transport.

Open flashcards full page
Unit 4 Interactive Review

Practice membrane structure, passive and active transport, osmosis, and interpreting cellular transport data.

Start Unit 4 review
Unit 4 Review Quiz

Complete 25 single-choice questions with immediate feedback, including membrane diagrams and transport data tables.

Start review quiz
Cell Membrane Permeability Review

Practice membrane structure, selective permeability, and movement across the cell membrane.

Open full page
Passive and Active Transport Review

Practice distinguishing passive transport from energy-requiring active transport.

Open full page
Osmosis Review

Practice predicting water movement and cell responses in different solutions.

Open full page
Label the Cell Membrane

Identify the major structures of the cell membrane.

Open full page
Blooket and Wayground Reviews

Open the Unit 4 section of the Biology Review Doc for Blooket games and Wayground reviews.

Open Unit 4 resources
Test 2 Flashcards - Units 3-4

Review Unit 3 and Unit 4 terms separately or as one mixed test deck.

Open test flashcards full page