Name________________________________________________________ Course and Section________________
Lab partner(s)__________________________________________________________________________________
Enter “none” on the line above if you worked alone.
Note – Do not turn in this answer sheet if you are submitting a formal lab report.
1. Table 1 – pH of water in the light and dark tubes
Time
pH - Light Tube
pH - Dark Tube
Initial reading
10
20
30
40
50
60
2.
Use graphing software such as Create A Graph or Excel to create a graph of your results from this experiment.
Put time on the X-axis and pH on the Y-axis. The title of the graph should be similar to what you would use in a
publication (or lab report). It should begin with “Figure 1. ” and it should provide enough information that the
reader can understand the graph without reading anything else about the lab.
Adjust the graph so that the minimum value of the Y-axis is a number that is slightly less than the minimum
value observed in the table above. The maximum value should be equal to or slightly greater than the maximum
value of the data. For example, suppose that the minimum pH that you measured was 5.9 and the maximum was
7.3. You could make the minimum on the graph 5.5 and the maximum 7.5.
Be sure that you clearly identify the two lines. For example, you could use circles for points on one line and
squares for points on the other line.
Attach the graph to this answer sheet before it is submitted.
3.
What will happen to the pH of water when CO2 is dissolved in the water?
4.
Write the equation that describes what happens when CO2 is dissolved in water.
5.
What will happen to the pH of water when CO2 is removed from the water?
6.
Two kinds of metabolic reactions caused the pH to change in the light tube. One of these processes caused the
pH to increase, the other caused it to decrease. Name these processes and tell which causes the pH to increase
and which causes the pH to decline.
7.
The two processes listed above had opposite effects on the pH. Why did the pH increase in the light tube if both
of these process were occurring at the same time?
8.
Explain why the values produced from the light tube do not reflect the total photosynthesis (total CO 2
consumption) of the plant. [Hint – Think about your answer to question #7.]
9.
Cellular Respiration was expected to cause the pH to decline in the dark tube but photosynthesis also occurred
in that tube. Name the part of photosynthesis that occurred in the dark tube.
10. Explain why the pH of the tube in the dark might increase early in the experiment before decreasing. Your
answer must mention the Calvin cycle. The diagram below may be helpful for answering this question.
H2O
light
O2
light reactions
ATP
NADPH
ADP
NADP+
light-independent reactions
(Calvin cycle)
C02
C6H12O6
11. Explain why the pH of the light tube might stop increasing toward the end of the 60 minute time period. The
diagram above may be helpful for answering this question.
12. Table 2 – Rf values of photosynthetic pigments using paper chromatography.
Distance
moved
Solvent
Rf
XXXX
Beta-carotenes
Xanthophylls
Chlorophyll a
Chlorophyll b
2