• 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: mineral ions entering root hairs from soil with fewer ions? (diffusion / osmosis / active transport) → active transportPrompt: Is it water specifically? Is it going against the gradient?
2. A poison stops respiration in root cells. Which process stops first? (active transport of mineral ions / osmosis of water / diffusion of oxygen / all three equally) → active transport of mineral ionsPrompt: Only one process needs energy from respiration.
3. Transport in cells: which statement is true? (Diffusion is faster when the gradient is steeper. / Osmosis needs energy from respiration. / Water moves by osmosis from a concentrated to a dilute solution. / Active transport only happens in plants.) → Diffusion is faster when the gradient is steeper.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: simple diffusion of oxygen through the phospholipid bilayer? (passive (no ATP needed) / active (uses ATP)) → passive (no ATP needed)Prompt: Does it go down a gradient by itself?
2. Why can oxygen cross the membrane easily but glucose needs a protein? (Glucose dissolves in fat / Glucose is a gas / Oxygen is small and non-polar; glucose is larger and polar / 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.

• 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. Is this passive or active transport: the sodium–potassium pump? (passive (no ATP needed) / active (uses ATP)) → active (uses ATP)Prompt: Does it go down a gradient by itself?
2. Cystic fibrosis is caused by a faulty chloride ion channel protein. What does this show? (Channel proteins carry oxygen / Ions cross membranes without help / Membrane proteins are vital for moving specific ions across membranes / Phospholipids are made of chloride) → Membrane proteins are vital for moving specific ions across membranesPrompt: Charged ions cannot pass through the fatty middle of the bilayer.

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