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© eScience Labs, 2018
Energy and Photosynthesis
PRE-LAB QUESTIONS
1. Describe how the functional units for beta carotene, xanthophyll, chlorophyll A, and
chlorophyll B are different. Be sure to identify the subunits that adhere to paper during
chromatography. Beta carotene- insoluble in water, soluble in alcohol as well as in
organic solvents, yellow pigment is called carotenoids. Xanthophyll- contains
hydroxyl or keto epoxide, yellow color comes from absorption of different shades,
peaking in the violet-blue region of the absorption spectrum.
2. Describe a technique for measuring photosynthetic rate. A light source is used to
illuminate a plant that is placed underwater. This is done at different distances
from the initial setup. You can then observe the rate at which gas is produced
from each distance. This tests the photosynthetic rate. Over time, a change in pH
can be noted as well.
3. Many deciduous trees have leaves that turn yellow in the fall. What do you suppose is
happening in the leaves at the cellular and molecular levels? There is a decrease in
chlorophyll production within the leaves. This is caused by a decrease in the
movement of nutrients throughout the tree because of environmental changes.
Carotenoids are responsible for the yellow color of the leaves.
4. Chloroplasts and mitochondria are both unusual in that they have double membranes
and contain their own set of DNA. Can you think of any explanations for this
observation? They have formed a symbolic bond with each other.
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Energy and Photosynthesis
EXPERIMENT 1: PAPER CHROMATOGRAPHY
Result Tables
Table 1: Chromatography Data
Solvent
Distance from Original Line to Solvent
Front
Number of
Bands
Rf Factor
Water
Solvent 25mm
Pigment 13 mm
1
Acetone
Solvent 59 mm
Pigment 37 mm
3
Mineral Oil
Solvent 30 mm
Pigment 0 mm
1
Acetic Acid
Solvent 40 mm
Pigment 11 mm
1
Table 2: Photosynthesis Data
Test Tube
Are
chloroplasts
present?
Initial Color
Final Color
1
No
Purple
Purple
2
Yes
Dark Blue
Dark Blue
3
yes
Dark Blue
Clear/ yellow
Post-Lab Questions
1. What did the different colored bands signify in each solvent for Part 1? What pigments
can you associate them with? Different pigments that are present in a spinach leaf,
chlorophyll A and B are associated with the green bands; carotene and
xanthophyll are associated with the yellow bands
2. What is the osmolarity fluid used in Part 2? Why is this important? Why is it essential to
keep it cool? The osmolarity fluid is 100 ml of sucrose solution. It is important
because it allows only the natural reaction of the leaves and prevents outside
sources from interfering. It is essential to keep it cool because it keeps the leaves
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© eScience Labs, 2018
Energy and Photosynthesis
from breaking down as well as not allowing any type of modification to the
chloroplasts.
3. How could you modify this experiment to show the effects of different wavelengths of
light on the photosynthetic rate? The light intensity can be used to modify this
experiment. Using a spectrofluorometer, one could test the pigment at different
wavelengths to gather more data.
4. Some plants (grasses) tend to contain a greater concentration of chlorophyll than others
(pines). Can you develop a hypothesis to explain this? Would it be testable? Different
CO2 concentrations can interfere with the rate of photosynthesis. The more CO2.
The more chlorophyll. This would be testable.
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