Measuring Respiration Rate in Yeast

Introduction

• Experiment to measure respiration rate in yeast using a test tube with yeast and glucose solution.
• Observation challenge: Yeast are tiny, and we can't visually detect respiration or gas production.

Glycolysis Overview

• Glycolysis in yeast cytoplasm:
  • Glucose broken down into pyruvate.
  • Requires 2 ATP, produces 4 ATP.
  • Involves oxidation (release of hydrogen atoms) and reduction (NAD accepts hydrogen, becomes reduced NAD).
• Glycolysis is invisible to the naked eye.

Redux Indicator

• Redux indicators help visualize respiration:
  • DCPIP (Dichlorophenol Indophenol) or Methylene Blue.
  • Both are non-toxic to yeast.
• Purpose: Prove respiration by color change during oxidation-reduction.

Experiment Procedure

• Add DCPIP or Methylene Blue to yeast and glucose solution.
• Initial color: Blue (original color of DCPIP).
• As glycolysis occurs, hydrogen atoms reduce DCPIP:
  • Reduced DCPIP becomes colorless.
  • Color change is visible, indicating respiration.

Temperature Effect on Respiration

• Set up two test tubes:
  1. Yeast at 10°C.
  2. Yeast at 20°C.
• Temperature influences enzyme activity:
  • 10°C: Slower respiration due to lower kinetic energy.
  • 20°C: Faster respiration due to higher kinetic energy.

Measuring Respiration Rate

• Start a stopwatch at the beginning of the experiment.
• Measure time for DCPIP to decolorize:
  • Yeast at 10°C decolorizes DCPIP slower than yeast at 20°C.
  • Example: 10°C yeast takes 150s, 20°C yeast takes 40s.
• Faster decolorization indicates higher respiration rate.

Conclusion

• Redux indicators like DCPIP and Methylene Blue allow for visual confirmation of yeast respiration.
• Temperature affects the respiration rate, with higher temperatures leading to faster rates.
• Both indicators function similarly in exams or experiments.