• Quick retrieval from earlier learning (Diffusion, osmosis or active transport?). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. Which process is this: urea passing from cells into the blood? (diffusion / osmosis / active transport) → diffusionPrompt: Is it water specifically? Is it going against the gradient?
2. Root hair cells contain many mitochondria. What does this suggest? (They do not respire / They photosynthesise / They use active transport, which needs energy / They absorb water only by diffusion) → They use active transport, which needs energyPrompt: What do mitochondria provide?
3. Transport in cells: which statement is true? (Osmosis needs energy from respiration. / Active transport can move substances from a low to a high concentration. / Active transport only happens in plants. / Water moves by osmosis from a concentrated to a dilute solution.) → Active transport can move substances from a low to a high concentration.Prompt: Which process needs energy?

• Show a microscope image of cells and ask what students think they are looking at.
• Share the objective: Membrane structure, protein channels and bulk transport. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Is this passive or active transport: a gland cell releasing hormone in vesicles (exocytosis)?
• Step 1: Active transport and bulk transport use energy from ATP.
• Step 2: So the answer is: active (uses ATP)
• Answer: active (uses ATP)
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. Is this passive or active transport: osmosis through aquaporin channels? (passive (no ATP needed) / active (uses ATP)) → passive (no ATP needed)Prompt: Does it go down a gradient by itself?
2. What are the two parts of a phospholipid molecule? (a protein and a sugar / a nucleus and a membrane / two heads and no tails / a hydrophilic (water-loving) head and two hydrophobic (water-fearing) tails) → a hydrophilic (water-loving) head and two hydrophobic (water-fearing) tailsPrompt: This is why phospholipids form a double layer in water.

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. Why can oxygen cross the membrane easily but glucose needs a protein? (Oxygen is small and non-polar; glucose is larger and polar / Glucose is a gas / Glucose dissolves in fat / Oxygen is too big for proteins) → Oxygen is small and non-polar; glucose is larger and polarPrompt: The middle of the bilayer is made of fatty tails.
2. Membranes: which statement is true? (The cell membrane is a phospholipid bilayer with proteins in it. / Large proteins pass through the membrane by simple diffusion. / Facilitated diffusion moves substances against their gradient. / Phospholipid tails are attracted to water.) → The cell membrane is a phospholipid bilayer with proteins in it.Prompt: Which processes need ATP?

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-12.