# Reserved first text alternative

Assign one file after feedback and a delay. Keep roles separate.

# Reserved new files · first response

Staff chooses one file after feedback and a delay. Learners use the assigned source/task only. Capture this first response before its matching later page. All numbers and descriptions are original conceptual models, not actual investigation results.


## E1 first

**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. It has no scale or full component inventory.

**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 permeability, temperature and pressure conditions, the moving substance and one unavailable outcome. Preserve first work before the later page.

# Reserved new files · first response

Staff chooses one file after feedback and a delay. Learners use the assigned source/task only. Capture this first response before its matching later page. All numbers and descriptions are original conceptual models, not actual investigation results.


## E2 first

**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. The complete membrane word map has water on each side, phospholipid bilayer, selective channel, external carbohydrate on glycoprotein and cholesterol among tails in a typical animal model; no scale or full component inventory is given.

**Task:** Explain J and K's mechanisms, directions and energy statements with evidence and the meaning of net movement. Explain head/tail orientation and the three listed component roles with a model limit. Explain the pouch's initial net water result and continuing molecular motion under the supplied permeability, temperature and pressure conditions; name an unavailable outcome. Preserve first work before the later page.

# Reserved new files · first response

Staff chooses one file after feedback and a delay. Learners use the assigned source/task only. Capture this first response before its matching later page. All numbers and descriptions are original conceptual models, not actual investigation results.


## F1 first

**Source:** Cube C has edge 4 mm; D has edge 8 mm. Area = 6a²; volume = a³; face-to-centre distance = a/2; SA/V = area/volume. 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, with independent model samples. Material, solution and endpoint rule match; temperature and stirring are unknown. Imposed layers and endpoint times are separate model descriptions.

**Task:** Calculate both areas, volumes, ratios with units and centre distances, and distinguish total surface from surface per volume. Calculate both fractions and average front speed, explaining why fraction is not intrinsic speed. Calculate both endpoint means/ranges; give a bounded comparison, missing condition and concrete improvement. State whether an actual learner investigation occurred. Preserve first work before the later page.

# Reserved new files · first response

Staff chooses one file after feedback and a delay. Learners use the assigned source/task only. Capture this first response before its matching later page. All numbers and descriptions are original conceptual models, not actual investigation results.


## F2 first

**Source:** Cube G has edge 2 mm; H has edge 4 mm. Area = 6a²; volume = a³; face-to-centre distance = a/2; SA/V = area/volume. 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, with independent model samples. Material, solution and endpoint rule match; temperature, stirring and measurement resolution are unknown. Imposed layers and endpoint times are separate model descriptions.

**Task:** Calculate both areas, volumes, ratios with units, centre distances, penetrated fractions and average front speed. Distinguish total surface from ratio and explain why fraction is not speed, including the zero-core/full-penetration case. Calculate means/ranges, compare the overlapping lists, name missing conditions or measurement information, and suggest an improvement. State whether an actual learner investigation occurred. Preserve first work before the later page.