# Ten teaching slots · 35 minutes each

Use the full science cards and the named worked contexts. Ordinary slots use **3 + 6 + 7 + 10 + 5 + 4 = 35 minutes**. The route period offers an initial response; extend it if needed. Worked contexts belong with staff when their solutions would give away the learner's task. All biological examples below are conceptual.

## Slot 11 · A boundary with several jobs

**Target:** connect the prerequisite cell ideas to a phospholipid bilayer and distinguish a membrane from a wall. **Prepare:** Cards A and B, contexts W01–W02, two parallel lines on paper.

- **Launch, 3 min:** Ask, “What separates a cell's inside from its surroundings? Does a wall replace that boundary?” Hear ideas before correcting them.
- **Model, 6 min:** Read the complete Leaf L and Bacterium B inventories. Both list a membrane. Put the plant wall outside it. Show heads facing water and tails facing each other in the animal membrane word map.
- **Guided work, 7 min:** Use W01 to find three shared features and the DNA-location difference. Then use W02 to correct a reversed-head drawing. Name the difference between a supplied diagram and a specimen.
- **Chosen route, 10 min:** Complete the slot 11 task in LEARNER.md using one of its three routes.
- **Discuss, 5 min:** Invite a learner to explain one placement. Ask whether an unlabelled protein in this simplified map must be absent in a real cell.
- **Exit, 4 min:** “A plant cell has a wall. Why does it still need a membrane?” Look for selective exchange at the cell boundary; wall and membrane are different structures. If heads/tails remain reversed, redraw the two watery sides before slot 12.

## Slot 12 · Which protein does what?

**Target:** explain channel, carrier, glycoprotein and cholesterol roles without making every protein a pump. **Prepare:** Card B, W03–W04, four full-word labels.

- **Launch:** Offer “Every membrane protein is a tunnel.” Ask what a reader would need to check.
- **Model:** Contrast a selective channel route with a glycoprotein's carbohydrate chain. Explain that a carrier can work passively or through energy coupling. Place cholesterol among the phospholipid tails in this animal model.
- **Guided work:** Model W03's job-based identification. In W04, compare two alternative captions and keep the condition-dependent cholesterol wording.
- **Chosen route:** Explain three component/function links and one limit.
- **Discuss:** Challenge “fluid means every component floats freely.” Learners correct it using lateral mobility with constraints.
- **Exit:** “Does finding a membrane protein prove active transport?” No. Ask for mechanism and energy/gradient evidence. Use a channel-versus-pump pair next if needed.

## Slot 13 · Molecules move; net movement has a direction

**Target:** infer neutral-substance direction from permeability and concentration, distinguishing simple and facilitated diffusion from the specified active pump. **Prepare:** Card C, W05–W06, outside/inside labels.

- **Launch:** Put 8 mmol/L outside and 2 mmol/L inside on paper. Ask what else is needed before drawing an arrow.
- **Model:** State Q's suitable passive carrier and inability to cross the bare bilayer. Draw net inward facilitated diffusion. Say particles can move both ways. Contrast the explicitly ATP-coupled inward R pump against its concentration difference.
- **Guided work:** Use W05 to compare Q, R and oxygen. Use W06 to explain equal-concentration dynamic equilibrium and the charged-ion information gap.
- **Chosen route:** Produce a three-case mechanism explanation and identify the insufficient-information case.
- **Discuss:** Test “The arrow tells us every molecule moves inward.” Learner changes it to net movement. Never infer an ion's passive direction from concentration alone.
- **Exit:** “What additional evidence turns a concentration difference into a useful neutral-solute prediction?” A specified permeable route and conditions. Reteach this before adding osmosis.

## Slot 14 · Water has its own question

**Target:** predict initial net water movement under explicit osmosis conditions and distinguish it from solute diffusion and vesicle transport. **Prepare:** Cards D and E, W07–W08, pouch outline.

- **Launch:** Ask what moves in osmosis: water, dissolved solute or the entire solution. Give time to choose and explain.
- **Model:** Mark water-permeable/solute-impermeable, equal temperature and equal initial pressure. For File O, draw initial water movement from 0.10 mol/L surroundings to the 0.30 mol/L pouch. Explain why a final volume has not been given.
- **Guided work:** Use W07 to reverse and balance the concentrations. Read W08's two complete vesicle frame sets; distinguish endocytosis and exocytosis from a molecule crossing a protein.
- **Chosen route:** Explain the pouch prediction and classify both frame sets with a reason.
- **Discuss:** Introduce unknown pressure as a reason to qualify the prediction; avoid treating more solute as a universal rule.
- **Exit:** “Can we predict a real plant cell's final size from these two concentrations alone?” No. Ask the learner to name one missing factor, such as pressure or permeability. Repeat a fully stated simple case before the check if needed.

## Slot 15 · Fresh Check E: the boundary display

**Target:** transfer membrane and transport reasoning to new supplied files; revise confidence after a new condition. **Prepare:** only Check E first page, a blank response sheet, then E later page kept separate.

- **Set up, 3 min:** Say, “Explain what the supplied conditions allow. An honest information gap is useful.” Record reading or response support.
- **Read source, 5 min:** Give E's complete first source. Clarify unfamiliar task vocabulary without identifying a mechanism or arrow.
- **First response, 12 min:** Complete Parts 1–3. A learner may use any response mode. Avoid directing their answer from the staff model.
- **Collect, 2 min:** Save, copy or mark the first response before giving later information. Identify it as first work.
- **Later response, 8 min:** Give the complete E later page. The learner revisits only the pouch conclusion, stating what changes and what remains supported. Keep both responses.
- **Reflect, 5 min:** Ask the learner to name the most useful next question. Use the separate key after capture and select one concrete teaching move. These responses are formative, not a QCAA unit result.

## Slot 16 · Bigger area, smaller ratio

**Target:** calculate cube surface area, volume and SA/V with units, then explain a size comparison. **Prepare:** Card F, W09–W10, calculator optional.

- **Launch:** Compare a 10 µm and 20 µm edge. Ask whether doubling length doubles area and volume.
- **Model:** Calculate 6 × 10² = 600 µm² and 10³ = 1,000 µm³ separately. Divide to get 0.60 µm⁻¹. Explain that the ratio is surface per volume.
- **Guided work:** Use W09 to establish fourfold area versus eightfold volume on doubling. Use W10 to explain why the larger cube still has more absolute surface.
- **Chosen route:** Solve a new edge-30 µm case and compare it with P.
- **Discuss:** Replace “large cells have less surface area” with “larger similar shapes have less surface area per unit volume.” Retain both correct quantities.
- **Exit:** “What are the units after µm² is divided by µm³?” µm⁻¹. If uncertain, practise cancelling the units in a separate line.

## Slot 17 · A shorter route to the centre

**Target:** link shape and exchange distance to function without claiming a universal size limit. **Prepare:** Card F, W11–W12, rectangle outline.

- **Launch:** Ask if two shapes with equal volume must have equal surface area or distance to the centre.
- **Model:** Contrast a 2 × 2 × 2 unit cube with a 1 × 2 × 4 unit rectangular model. Same volume, different surface area and nearest-face distance.
- **Guided work:** Work W11's full geometry. W12 compares a smooth patch with a folded patch, keeping the projected footprint and membrane area separate.
- **Chosen route:** Explain one size/shape adaptation and one condition the model leaves open.
- **Discuss:** “More folds mean every kind of substance will cross faster.” Correct it: extra surface may help when permeability and gradients permit exchange; other limitations remain.
- **Exit:** “Why can a thin shape help exchange?” A shorter diffusion path, with the relevant supplied geometry. Follow with a labelled centre-distance sketch if area is being confused with distance.

## Slot 18 · Same depth, different fraction

**Target:** calculate fraction penetrated and distinguish it from average front speed. **Prepare:** Card G, W13–W14, four arithmetic lines for each cube.

- **Launch:** Ask which would have more of its volume reached by the same 0.5 mm layer: a 2 mm or 8 mm cube.
- **Model:** For 2 mm, central edge = 2 − 2 × 0.5 = 1 mm. Fraction penetrated = 1 − 1³/2³ = 0.875. Label this as a fraction at a time.
- **Guided work:** Work W13's 4 mm case. State d_start = 0 mm at t_start = 0 min. In W14, use Δdepth/Δtime = (d_end − d_start)/(t_end − t_start): (0.5 − 0) mm / (4 − 0) min for both sizes. This interval average is not a constant future speed, intrinsic diffusion coefficient or molecular flux.
- **Chosen route:** Calculate the fraction for a 6 mm cube at depth 1 mm; state whether this proves an intrinsic diffusion speed.
- **Discuss:** Check whether the “twice the layer” subtraction was made on both opposite faces. Clamp a negative central edge to zero for full penetration.
- **Exit:** “Which result has mm/min units?” Average change in depth divided by elapsed time, not fraction penetrated. If needed, teach unit labels before another calculation.

## Slot 19 · What would make a comparison useful?

**Target:** summarise supplied repeats and evaluate a proposed diffusion comparison, retaining uncertainty. **Prepare:** Card H, W15–W18, blank variable and evidence table.

- **Launch:** Present two endpoint times measured with different temperatures. Ask whether size alone explains their difference.
- **Model:** Use W15 to identify that confound. Name independent size, a defined dependent endpoint/time, and constant conditions. Distinguish a proposed experiment from a completed one.
- **Guided work:** W16 calculates means/ranges; W17 interprets overlap; W18 considers a consistent timing bias. Treat the numbers as invented examples.
- **Chosen route:** Improve Plan H with an explicit endpoint, independent repeats, one measurement limitation and a bounded conclusion.
- **Discuss:** Ask whether repeats fix an instrument that always adds 5 seconds. Retain variation and bias as different concerns.
- **Exit:** “What would you need to call these actual investigation results?” A documented actual method/system, samples or virtual runs, observations and conditions; an authored table alone is insufficient. Next teaching may be a locally approved real/virtual practical.

## Slot 20 · Fresh Check F: the cube comparison

**Target:** transfer geometry and evidence reasoning to unfamiliar dimensions, then judge a new comparison condition. **Prepare:** only F first page; F later page separate; neutral cube outline permitted.

- **Set up, 3 min:** Explain that calculation, claim and limitation all matter. Record calculator and source-reading support.
- **Read source, 5 min:** Give the complete first page. Read units aloud if needed without supplying a calculation.
- **First response, 12 min:** Complete Parts 1–3. Capture the learner's ratio, fraction and evidence judgement.
- **Collect, 2 min:** Preserve the first work before the later page appears.
- **Later response, 8 min:** Give the complete F later page. Reconsider the confidence in a size-only comparison using the newly disclosed conditions. Separate unchanged geometry from weakened causal inference.
- **Reflect, 5 min:** Ask for one next measurement or design improvement. After collection, compare with the separate staff model. Choose one targeted reteach and reserve F1/F2 for a delayed unseen response. No practical or whole-topic mastery follows from a successful paper check.

## Two last contexts for flexible discussion

Use W19 after E feedback to combine a membrane mechanism and a cell-demand explanation. Use W20 after F feedback to compare competing captions. They provide a different setting for consolidating the fortnight; they are not extra compulsory sessions.