Organisms, pH and Buffers
Investigating the ability of various solutions to resist pH changes in order to determine how living creatures survive.
PASPORT pH Sensor
(PS-2102)
ScienceWorkshop pH Sensor
(CI-6507A)
Lab Summary
Students will investigate the ability of various solutions to resist pH changes in order to determine how living creatures survive and maintain homeostasis despite biochemical activities that alter pH.
All living creatures, even single-celled organisms, must maintain very stable internal conditions in order to survive. Even as the metabolic environment changes, an organism must sustain physiological conditions such as temperature, pH, water content, and food intake at healthy levels. This stable level of metabolic conditions is called homeostasis, and organisms maintain homeostasis in a variety of ways. In multicellular organisms, complex buffer systems allow the organism to maintain internal pH, avoiding excessive acidity or excessive alkalinity. Scientists use the pH scale to describe how acidic or alkaline a substance is. Substances with a pH of 7 are neutral, while substances with a pH lower than 7 are acidic and those with a pH greater than 7 are alkaline (basic). Because the pH scale is logarithmic, each change of 1 pH unit on the scale corresponds to a ten-fold difference in acidity: therefore a solution with a pH of 2 is ten times more acidic than a solution with a pH of 3.
Hypothesize: How do organisms survive and function despite metabolic activities that tend to shift pH toward either the acidic or basic ends of the scale?
Published: October 2002
Downloads
- Organisms, pH and Buffers - PASPORT (40 KB, .zip)
Includes experiment setup, procedures and Datastudio file
- Organisms, pH and Buffers - ScienceWorkshop (41 KB, .zip)
Includes experiment setup, procedures and Datastudio file
Here's What You Need
U.S. Educator prices shown.
Probeware (PASPORT Systems)
Xplorer GLX (PS-2002) - $349
The Xplorer GLX is a data collection, graphing, and analysis tool designed for science students and educators.
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.
Probeware (ScienceWorkshop Systems)
750 Interface, USB (CI-7650) - $679
The 750 Interface allows students to measure force, temperature, pressure, angular velocity, acceleration, current, and magnetic field with a built-in function generator and oscilloscope mode.
Other Materials
- 0.1 M HCl solution, approximately 10 mL total volume
- 0.1 M NaOH solution, approximately 10 mL total volume
- Lab glassware: 50-mL beaker, 50-mL graduated cylinder, dropper bottles or eyedroppers, wash bottle and waste container
Test solutions: 25 mL each of the following: (See Teacher's Hints for recipes) --Tap water, Liver homogenate, Potato homogenate, Egg white, Gelatin, Sodium phosphate buffer solution, 0.01 M, pH 7.2
