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About This Drill
AP Biology — Unit 3 — Cellular Respiration: Glycolysis & Krebs Cycle — Drill 12 is a practice drill. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.
Analyze a respirometer experiment measuring oxygen consumption in germinating pea seeds. Interpret quantitative data, evaluate experimental design, and connect cellular respiration rates to oxygen availability and ATP production.
Passage
A researcher designed an experiment to measure cellular respiration rates in germinating pea seeds under varying oxygen concentrations. Germinating seeds were placed in sealed respirometers containing a KOH solution to absorb CO2. The change in gas volume inside each respirometer over 30 minutes reflects net O2 consumption. Three oxygen treatment levels were tested at 22C.
Table 1. Net O2 consumed (mL) over 30 minutes at three oxygen concentrations.
| O2 Concentration (%) | Trial 1 | Trial 2 | Trial 3 | Mean |
|---|
| 2 | 0.9 | 1.1 | 0.8 | 0.93 |
| 10 | 2.4 | 2.6 | 2.3 | 2.43 |
| 21 (ambient) | 3.8 | 4.1 | 3.9 | 3.93 |
A control respirometer containing boiled (dead) seeds was run simultaneously at each oxygen concentration and showed no change in gas volume.
Questions in This Drill
- Based on the data in Table 1, what is the relationship between O2 concentration and cellular respiration rate in the germinating seeds?
- What was the purpose of the control respirometer containing boiled seeds, and what result would falsify the experiment's conclusions?
- If the experiment were repeated at 4C instead of 22C, which outcome would be most expected, and why?
- During aerobic cellular respiration at 21% O2, which stage produces the greatest number of ATP molecules per glucose molecule?
- The researchers used KOH solution in the respirometers. What would happen to the data if the KOH were accidentally omitted from the experimental respirometers?