Question 1
Paper 2Medium16 marksA researcher investigated the movement of different solutes across a model phospholipid bilayer. The same apparatus was used for separate trials, one solute per trial. Figure 1 shows the initial conditions for each trial. After 30.0 minutes, the amount of solute detected in chamber B was measured.
| Solute tested | Description | Amount detected in chamber B after 30.0 min / nmol |
|---|---|---|
| Steroid | Non-polar molecule | 15.2 |
| Glucose | Polar molecule | 1.6 |
| Sodium ions | Ions | 0.8 |
| Polymer | Large, hydrophilic molecule | 0.2 |
State the independent variable, the dependent variable and one variable controlled in the investigation.
Calculate the percentage of the initial amount of steroid detected in chamber B after 30.0 minutes.
Compare the amounts detected in chamber B for the four solutes.
Explain how the structure of the phospholipid bilayer accounts for the results for the steroid and the other three solutes.
A student concludes that the bilayer is an effective barrier to every solute tested. Evaluate this conclusion using the data.