Passage I

In certain solutions, beet cells undergo membrane disruption, causing the cells to release betacyanin (a red pigment). As membrane disruption increases, more, betacyanin is released. To determine the amount of betacyanin released, the amount of light absorbed (at a specific wavelength) by the solution is measured. As the concentration of betacyanin in the solution increases, the amount of light absorbed increases.

To determine the amount of light absorbed by a solution, light is directed through a sample of the solution onto a detector (see Figure 1).

By measuring the amount of light that hits the detector, the amount of light absorbed by the sample can be determined.

Experiment 1

For each of 9 trials, a student placed a beet section (2 cm x 2 cm x 1 cm) in 100 mL of water at a specific temperature for 10, 20, or 30 min. The student then removed a sample of the solution and determined its absorbance (see Table 1).

Experiment 2

Experiment 1 was repeated, except that in each trial an acetone/water solution was used instead of water and the temperature was kept constant at 25°C (see Table 2).

Experiment 3

Experiment 2 was repeated, except that in each trial a methanol/water solution was used instead of an acetone/water solution (see Table 3).

The student then determined the absorbance of water, of acetone, and of methanol. Each had an absorbance of 0.00.