A student measures cellular respiration in germinating peas using a respirometer. A respirometer contains peas, KOH-soaked cotton (to absorb CO2), and a glass tube with a colored water droplet. As peas consume O2 and CO2 is absorbed, the droplet moves toward the peas. Three respirometers are set up: (A) germinating peas, (B) dry/dormant peas with glass beads to equal volume, (C) glass beads only. All are immersed in a 25 C water bath.
What is the role of respirometer C (glass beads only)?
- Acheck_circle
A control to detect changes due to temperature or pressure unrelated to respiration
- B
An indicator of CO2 production
- C
A negative control for KOH activity
- D
A measure of dormant pea respiration
Explanation
The bead-only tube cannot respire. Any droplet movement reflects nonbiological causes (temperature drift, atmospheric pressure changes). This baseline is subtracted from the experimental readings.