The question
Name: ______________________ Date: ____________ Heat and leakage from beet cells (9 points)
Data table
Heat and leakage from beet cells
Beet root cells store a red, water-soluble substance in a large central vacuole surrounded by a membrane, inside a cell enclosed by the plasma membrane. Researchers cut 24 identical cubes from one beet and rinsed them. They heated groups of six cubes for 1 minute in water baths at 30, 45, 60 or 75 °C, then placed each cube in 10 mL of distilled water at room temperature for 20 minutes. They measured how red the water became as absorbance (higher absorbance means more of the red substance in the water).
| Heating temperature (°C) | Mean absorbance (arbitrary units) | Standard error of the mean, SE |
|---|---|---|
| 30 | 0.10 | 0.02 |
| 45 | 0.16 | 0.03 |
| 60 | 0.52 | 0.04 |
| 75 | 0.81 | 0.05 |
(A) Explain why little of the red substance leaves an undamaged beet cell. [1 point]
(B) (i) Identify the independent variable in the experiment. (ii) The researchers treated the 30 °C group as a control. Justify this choice by stating what it allows them to rule out. [2 points]
(C) Construct an appropriately labeled graph that shows the mean absorbance at each temperature, with error bars showing the 95% confidence interval (mean ± 2SE). [4 points]
(D) (i) Based on your graph, determine whether heating to 45 °C caused more leakage than heating to 30 °C, and justify your answer. (ii) Explain the large increase in leakage between 45 °C and 75 °C in terms of membrane structure. [2 points]