P05-a · 2 actual pages
Check E · The boundary display
Complete first source E
The display represents a simplified typical animal plasma membrane. Water lies outside and in the cytoplasm. It includes phospholipids, a selective channel, a glycoprotein with a carbohydrate chain facing outside, and cholesterol among the lipid tails. This is a word model, not a micrograph; component spacing and complete composition are not supplied.
Neutral U is 6 mmol/L outside and 2 mmol/L inside. U cannot cross the bare bilayer but can use a suitable passive carrier. Neutral V is 3 mmol/L outside and 7 mmol/L inside. A specified ATP-coupled protein pump carries V inward. The values are invented model conditions.
A separate flexible pouch contains 0.40 mol/L of one neutral solute; the surrounding solution contains 0.15 mol/L of the same solute. Water can cross its membrane; this solute cannot. Initial temperature and hydrostatic pressure are equal on both sides. No final volume, duration or real-cell survival information is supplied.
Complete first task E
- For U and V, name the transport mechanism, net direction, relevant concentration evidence and energy statement. Explain why a net arrow does not mean every molecule moves in that direction.
- Describe how phospholipid heads and tails face the watery spaces. Explain one role each for the channel, glycoprotein and cholesterol in this animal model. Give one limit of the display.
- Predict initial net water movement for the pouch. State the permeability, temperature and pressure conditions that make that prediction possible. Explain what moves by osmosis and one result you cannot infer.
Stop here. Preserve the first work before reading E's later page.
P07-a · 1 actual pages
Complete first source F
Two cubic geometric cell models have edges A = 3 mm and B = 6 mm. For a cube, surface area = 6a²; volume = a³; SA/V = surface area divided by volume; face-to-centre distance = a/2. These model sizes are chosen for readable arithmetic; they are not measured cell dimensions.
At 2 minutes the supplied idealised layer depth is 0.5 mm from every face of each cube. 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. This one-time imposed layer is not a universal diffusion law.
A second supplied endpoint-time file, for those same edge groups but a different hypothetical comparison, lists A: 40, 44, 48 s and B: 88, 92, 96 s. Its endpoint rule, material and external solution are specified as the same. Each value is labelled an independent model sample. Temperature and stirring details are not supplied. These are invented numbers, not experimental measurements. The endpoint-time table and the imposed-layer calculation are separate model descriptions; do not mix their time measures.
P07-b · 2 actual pages
Check F · The cube comparison
Complete first source F
Two cubic geometric cell models have edges A = 3 mm and B = 6 mm. For a cube, surface area = 6a²; volume = a³; SA/V = surface area divided by volume; face-to-centre distance = a/2. These model sizes are chosen for readable arithmetic; they are not measured cell dimensions.
At 2 minutes the supplied idealised layer depth is 0.5 mm from every face of each cube. 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. This one-time imposed layer is not a universal diffusion law.
A second supplied endpoint-time file, for those same edge groups but a different hypothetical comparison, lists A: 40, 44, 48 s and B: 88, 92, 96 s. Its endpoint rule, material and external solution are specified as the same. Each value is labelled an independent model sample. Temperature and stirring details are not supplied. These are invented numbers, not experimental measurements. The endpoint-time table and the imposed-layer calculation are separate model descriptions; do not mix their time measures.
Complete first task F
- Calculate each cube's surface area, volume, SA/V with units, and face-to-centre distance. Explain the difference between total surface and surface per unit volume.
- Calculate each fraction penetrated at 2 minutes and the average front speed. Explain why a larger fraction does not establish a larger intrinsic diffusion speed.
- For the separate endpoint-time file, calculate each mean and range. Give a supported comparison of the listed numbers, name an important missing condition, and suggest one way to improve the comparison. State whether an actual learner investigation has occurred.
Stop here. Preserve the first work before reading F's later page.