On a Scale of 0 to 14
(pg.182-188)
Define:
pH:
homogenates:
Part A: pH Is Everywhere
1) If you compared 2 solutions, 1 with a pH of 6 and another
with a pH of 5, what would be the difference?
Solution
Predicted pH
Actual pH
Questions:
1) Do any of the pH measurements differ from your predictions?
2) Which of the solutions that you tested could be harmful to the pH balance
of your organ systems? Why?
Part B: Regulating pH
Design a procedure to investigate how living cells regulate pH.
Procedure (Read the protocol on pg. 185):
In the graph below, draw a prediction of how you think pH will
change for both water and your homogenate when you add acid.
Then draw a prediction of how you think pH will change for
both water and your homogenate when you add base.
Write a brief justification for your prediction.
Perform the experiment from your designed procedure and
record the data in the table below:
Tests with 0.1 M HCl
Tests with 0.1 M NaOH
Solution pH after addition of drops
Tested
0
5
10 15 20 25
pH after addition of drops
0
5 10 15
20
25
Graph your data below:
Analyze your data (i.e. what is the pattern in the data? What is
this pattern telling us?):
Analysis Questions:
1) How is the homogenate response to the addition of acid and base similar to
or different from the way the water responded?
2) Based on your results and using water as a comparison, do you think potato
and liver cells are buffered? Explain your answer.
3) Is it likely that all living systems contain buffers? Why or why not?
4) At what pH do you think living liver and potato cells function best? On
what do you base this inference?
5) Based on your data from the experiment in Part B, how might a buffer help
maintain homeostasis? Explain your answer.
6) Many manufacturers claim that their health care and hair care products are
pH balanced or buffered. How would you test this claim?
LAB WRITE-UP
Testable Question
Hypothesis
Materials
Variables:
Procedure:
Data Table
Include your prediction and actual graph here as well as your data table for both acids and bases.
Analysis:
What does your data tell us?
Conclusion:
Write a conclusive statement that answers the testable question.
Using data from the lab (be sure to include the high and low data point) support your analysis
Use explanatory language to connect or compare the data to support your conclusive statement