# Four unused rechecks · staff reserve

This staff-only planning overview contains complete first/later source material together. For actual learner handout, choose the separate clean source for the needed case: [E1 first](../reserve/first/E1.md), [E2 first](../reserve/first/E2.md), [F1 first](../reserve/first/F1.md) or [F2 first](../reserve/first/F2.md). Collect the first response before supplying the matching [E1 later](../reserve/later/E1.md), [E2 later](../reserve/later/E2.md), [F1 later](../reserve/later/F1.md) or [F2 later](../reserve/later/F2.md) source. Do not hand out this combined overview before collection. Keep rechecks for a delayed new encounter after targeted feedback. Do not use them as taught examples first. Select a recheck for the particular skill; they are not secure exams or equivalent whole-unit instruments. Capture response and support before discussing the separate key.

## E1 · A second boundary file

**Complete source:** Neutral N is 9 mmol/L inside and 3 mmol/L outside, cannot cross the bare bilayer and has a suitable passive carrier. Neutral P is 2 mmol/L inside and 5 mmol/L outside; an ATP-coupled pump carries P outward. A separate pouch has 0.12 mol/L impermeant neutral solute inside and 0.28 mol/L outside. Water crosses; solute does not; temperature and initial hydrostatic pressure are equal. A word map describes water on both sides of a phospholipid bilayer, a channel, an external carbohydrate chain on a glycoprotein and cholesterol among tails in an animal model. Values and map are original conceptual material.

**Complete task:** For N and P give mechanism, net direction, concentration evidence and energy statement; explain net movement. Describe head/tail orientation, one role each for channel, glycoprotein and cholesterol, and a model limit. Predict initial net water movement for the pouch, naming all stated conditions, the moving substance and one unavailable outcome. Then consider the same pouch with unknown pressure difference: qualify the water prediction and request the needed information.

## E2 · An equal-concentration pouch

**Complete source:** Neutral J is 4 mmol/L outside and 1 mmol/L inside and can cross the bilayer. Neutral K is 2 mmol/L outside and 6 mmol/L inside; a specified ATP-coupled pump carries K inward. A separate pouch has 0.22 mol/L impermeant neutral solute both inside and outside; water can cross, solute cannot, and initial temperature/pressure are equal. Use the complete membrane word map: water on each side, phospholipid bilayer, selective channel, external carbohydrate on glycoprotein, cholesterol among tails in a typical animal model. Values and map are supplied teaching models.

**Complete task:** Explain J and K's mechanisms/directions/energy with evidence and the meaning of net movement. Explain head/tail orientation and the three listed component roles with a limit. Explain the pouch's initial net water result and continuing molecular motion under the supplied conditions; name an unavailable outcome. In a new pressure-unknown scenario with the same equal solute values, state whether no net water movement can still be asserted with certainty and what information is needed.

## F1 · Two larger paper cubes

**Complete source:** Cube C has edge 4 mm; D has edge 8 mm. Area = 6a²; volume = a³; distance = a/2. Each has a supplied layer 1 mm deep at 5 min. Central edge = max(a − 2d, 0); fraction penetrated = 1 − (central edge/a)³; For this supplied interval, the layer starts at depth d_start = 0 mm when t_start = 0 min. Average front speed = Δdepth/Δtime = (d_end − d_start)/(t_end − t_start). This is the model's interval average, not a constant future speed, intrinsic diffusion coefficient or molecular flux. In a separate supplied endpoint file C has 70, 74, 78 s and D 130, 134, 138 s. Material, solution and endpoint rule match; temperature/stirring are initially unknown. Later plan notes say C was 18°C and D 28°C, with unstandardised stirring. All data are original conceptual examples; no experiment was performed.

**Complete task:** Calculate both areas, volumes, ratios with units and centre distances. Calculate both fractions and average front speed, explaining why fraction is not intrinsic speed. Calculate means/ranges in the separate endpoint file and give a bounded comparison, missing condition and improvement. After a first response is captured, release the later temperature/stirring notes from the source above and request a second response: keep or revise the claim with reasons; name the unchanged geometry, confounds, defined dependent measure and independent-repeat improvement. Staff must supply the initial source with the sentence beginning “Later plan notes” withheld until first capture.

## F2 · Full penetration is a boundary case

**Complete source:** Cube G has edge 2 mm; H has edge 4 mm. Area = 6a²; volume = a³; distance = a/2. Each has a supplied layer 1 mm deep at 4 min. Central edge = max(a − 2d, 0); fraction penetrated = 1 − (central edge/a)³; For this supplied interval, the layer starts at depth d_start = 0 mm when t_start = 0 min. Average front speed = Δdepth/Δtime = (d_end − d_start)/(t_end − t_start). This is the model's interval average, not a constant future speed, intrinsic diffusion coefficient or molecular flux. In a separate supplied endpoint file G has 80, 90, 100 s and H 90, 100, 110 s. Same material, solution and endpoint rule; temperature/stirring initially unknown. Later plan notes give equal temperature and standardised stirring, but the endpoint judgement used an instrument with resolution 10 s. All values are invented examples, not observations.

**Complete task:** Calculate both areas, volumes, ratios, centre distances, penetrated fractions and average front speed. Explain the zero-core/full-penetration case and why this says no more than the supplied geometry. Calculate both means/ranges, compare the overlapping lists and name a missing condition or measurement detail. Capture first work before the later sentence is released. Then judge whether equal temperature/stirring removes every limitation; explain how the coarse endpoint resolution affects confidence and propose a better recorded measure. Keep a valid cautious claim or revise an overstatement; retain the geometry. Staff initially withhold the sentence beginning “Later plan notes”.