Author: Biology Junction Team

Cell Membrane Coloring Sheet: Labels, Transport, and Teaching Notes

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

Use coloring to reveal membrane organization, then require students to explain what the pattern means. Students can use written labels or textures instead of color. Begin after an introduction to phospholipids and cell boundaries.

Objectives and materials

Students will distinguish hydrophilic heads from hydrophobic tails, orient a bilayer relative to water, and separate membrane structure from transport mechanism. Materials: the existing Word worksheet or plain paper for the original task below, pencils, and optional coloring supplies.

Existing worksheet download

Download the Cell Membrane Coloring Worksheet (Word .doc). The file includes fill-in sections on membrane composition, diagram-labeling and color prompts, tonicity, and energy-requiring transport. Open it in compatible word-processing software and check that the diagrams print before making class copies. No verified answer key is supplied here.

Teacher corrections for the legacy file

  • Cholesterol buffers membrane fluidity; its effect depends on temperature and membrane conditions, so “always makes the membrane more fluid” is incomplete.
  • An integral protein need not span the entire bilayer. A transmembrane protein does.
  • Water can cross the bilayer, and aquaporin channels can greatly increase water permeability. Do not teach that all water movement is simple passage through lipids.
  • Tonicity depends on effectively nonpenetrating solutes relative to a particular cell. Describe which solutes can cross before interpreting a diagram.
  • Turgor pressure and osmotic pressure are related but different quantities. Plasmolysis is membrane withdrawal from the plant cell wall after water loss, not every decrease in turgor.

Original on-page drawing task

  1. Draw two rows of phospholipids. Use circles for heads and two short lines for tails. Put tails toward the interior and heads toward the water on both sides.
  2. Label outside fluid, cytoplasm, hydrophilic head, hydrophobic tails, and bilayer. Add a legend with both colors and words.
  3. Add one transmembrane channel and one surface-associated protein. Label them without implying that every membrane protein is a channel.
  4. Add a carbohydrate chain on the extracellular side, attached to a protein or lipid.
  5. Draw one arrow for a small nonpolar molecule crossing the lipid region and a separate arrow for an ion using an open channel. State the gradient assumed for each arrow.
  6. Write two sentences explaining why an ion does not readily cross the hydrophobic interior unaided.

Discuss and check

Why do heads face water on both sides? Their polar character allows favorable interactions with water; the nonpolar tails form the interior. Does a channel make transport active? No. Movement down an electrochemical gradient through a channel is passive. What does the drawing omit? It is a static cross-section; it does not show molecular motion or realistic dimensions.

Teaching note: Ask for explanations before assessing neatness. The drawing task can be printed using the browser or completed in a notebook. For AP biology, add a prediction about how a change in membrane composition could affect fluidity, naming the conditions needed.

Continue the unit

Sources and further reading