Organisms and pH
Measure the buffering capacity of some biological materials in solution by comparing the ability of each sample to resist changes in pH when a strong acid or base is added. The sample solutions will be compared to negative (water) and positive (sodium phosphate buffer) controls.
Challenge your students to find the substance that is best able to resist changes in pH.
Lab Summary
In this exploration, students will use a pH sensor to study the effect of buffer solutions on pH. Students will measure the effect of acids and bases when added to various biological substances (e.g. egg white, liver homogenate, and potato homogenate).
Theory
In order to survive within a narrow range of acceptable pH levels, organisms must posess the ability to buffer solutions. By adding acid or alkali and measuring the change in pH this ability can be studied as it pertains to different biological compounds.
Downloads
- Computer-based lab (PDF, 472 KB) (472 KB, .pdf)
(student version)
- Xplorer GLX-based lab (PDF, 792 KB) (724 KB, .pdf)
(student version)
Method
Use the pH Sensor to study the effect of buffer solutions on pH.
Here's What You Need
U.S. Educator prices shown.
Probeware
PASPORT pH Sensor (PS-2102) - $79
Has a wide measurement range of 0 to 14 pH. Has a resolution of 0.01 pH. For use with PASPORT Interfaces.
Xplorer GLX (PS-2002) - $349
The Xplorer GLX is a data collection, graphing, and analysis tool designed for science students and educators.
Other Materials
- Beaker, 50-mL
- Graduated Cylinder, 100-mL
- Dropper bottles
- Wash bottle
- Waste container
- Water, 50.0 mL
- Liver Homogenate, 25.0 mL
- Potato Homogenate, 25.0 mL
- Egg White Solution, 25.0 mL
- Gelatin Solution, 25.0 mL
- Sodium Phosphate Buffer (Na2HPO4), 0.01 M, 25.0 mL
- Hydrochloric Acid (HCl), 0.1 M, 100.0 mL
- Sodium Hydroxide (NaOH), 0.1 M, 100.0 mL
