1D · Diffusion Parameters Simulation
This lecture runs a simulation of the factors from 1C. Three parameters are adjustable: the molecular weight of the solute, the temperature, and the size of the concentration gradient between two fluid compartments. Solution strength is labeled in percent, so a trial might run 5% solute against 0% plain water.
Each trial produces a diffusion rate from two numbers taken at equilibrium.
The concentration change is always half the starting gradient, since equilibrium lands in the middle. The unit, percent solute per second, is odd, but it is what the simulation gives and it is consistent across trials.
Trial 1 sets the baseline: medium-size solutes, 5% on side A against 0% on side B, at 40°C, the closest the simulation gets to normal body temperature of 37°C.
Four trials, one parameter changed at a time
Trial | Solute size | Temp | Gradient | Δ[solute] | Time | Rate (%/s) |
|---|---|---|---|---|---|---|
1 · baseline | Medium | 40°C | 5% | 2.5% | 262 s | 0.0095 |
2 · smaller solute | Small | 40°C | 5% | 2.5% | 79 s | 0.0316 |
3 · cooler | Small | 30°C | 5% | 2.5% | 111 s | 0.0225 |
4 · smaller gradient | Small | 40°C | 2% | 1.0% | 61 s | 0.0164 |
Size. Small solutes diffused more than three times faster than medium ones under identical conditions. Molecular weight sits in the denominator, and the simulation confirms it.
Temperature. Dropping from 40°C to 30°C stretched equilibrium from 79 s to 111 s. Less heat energy in the system means slower molecular movement overall, so cooler temperatures slow diffusion.
Gradient. Halving the gradient from 5% to 2% cut the rate roughly in half, from 0.0316 to 0.0164. Note that time to equilibrium actually fell, from 79 s to 61 s, because there was less distance to close. The rate is what dropped.
Not every parameter was testable here, but these are the ones that genuinely vary in the body. We see diffusion of both large and small molecules, glucose versus sodium ions. We see diffusion under different temperature conditions, fever versus healthy. And transmembrane gradient magnitudes fluctuate constantly with diet, breathing, and metabolism.