Week 9 Photosynthesis XXXXXXXXXXBIOL XXXXXXXXXXCourse Content Unit 3 - Weeks 9 - 12
Page 6 of 7
Absorption Spectrum of Chloroplast Extract
1. Based on your observations, which wavelength
(color) of light might be expected to generate the
lowest rate of photosynthesis? _________
An instrument called spectrophotometer can be
used to pass light of specific wavelengths through
a sample of chloroplast pigments dissolved in a
solvent (you can review the module on
spectrophotometers from earlier in the term). The
degree of absorption of each of the wavelengths
of light by the pigments can then be measured.
The resultant data can be plotted on a graph,
thus producing an absorption spectrum of the
pigment mixture. Since all green plants don't
have exactly the same type and amount of
photosynthetic pigments, the spectra may vary
from one species of plant to another.
The pigment solution is prepared by mixing
several plant leaves with acetone and then
homogenizing them in a blender. Acetone is a
nonpolar organic solvent in which the pigment
molecules are soluble. This mixture is then filtered
to remove all de
is. The biology lab technician
has already prepared the mixture for you. The
solvent is extremely flammable, so use caution in
handling both the pigment solution and the
solvent.
Record the abso
ance for the specific
wavelengths given in the Table 3. You should
cali
ate (blank) the spectrophotometer every time
you change the wavelengths. Note this data is
provided for you in Table 3.
Table 3: Absorption Spectrum Data fo
Spinach Chloroplast Extract
Wavelength Abso
ance Wavelength Abso
ance Wavelength Abso
ance
380 nm
0.725
500 nm
0.139
620 nm
0.100
400 nm
0.834
520 nm
0.074
640 nm
0.135
420 nm
0.971
540 nm
0.047
660 nm
0.406
440 nm
0.844
560 nm
0.041
680 nm
0.049
460 nm
0.678
580 nm
0.059
700 nm
0.029
480 nm
0.338
600 nm
0.079
720 nm
0.000
Using Excel make a graph of the abso
ance versus the
wavelength.
Underneath the graph in your Excel spreadsheet answe
these two questions:
My Blackboard Courses Community
Page 6 of 7
Table of Contents
Learning Objectives
Background Information
Photosynthesis Pre-lab Quiz
Effect of Light Intensity on the Rate of Photosynthesis
Separation of Chloroplast Pigments by Paper Chromotography
Absorption Spectrum of Chloroplast Extract
Photosynthesis La
Henry Tolbert
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2. Based on your observations, which wavelength
(color) of light might be expected to generate the
highest rate of photosynthesis? _________
3. Why are plants typically green?
4. Photosynthesis produces the oxygen (O ) on which
all aerobic organisms depend for survival. What
other factors make photosynthesis essential to the
maintenance of virtually all life on earth?
2
absorption-spectrum-of-chloroplast-extract XXXXXXXXXXr1cmyda0.pdf
Week 9 Photosynthesis XXXXXXXXXXBIOL XXXXXXXXXXCourse Content Unit 3 - Weeks 9 - 12
Page 6 of 7
Absorption Spectrum of Chloroplast Extract
1. Based on your observations, which wavelength
(color) of light might be expected to generate the
lowest rate of photosynthesis? _________
An instrument called spectrophotometer can be
used to pass light of specific wavelengths through
a sample of chloroplast pigments dissolved in a
solvent (you can review the module on
spectrophotometers from earlier in the term). The
degree of absorption of each of the wavelengths
of light by the pigments can then be measured.
The resultant data can be plotted on a graph,
thus producing an absorption spectrum of the
pigment mixture. Since all green plants don't
have exactly the same type and amount of
photosynthetic pigments, the spectra may vary
from one species of plant to another.
The pigment solution is prepared by mixing
several plant leaves with acetone and then
homogenizing them in a blender. Acetone is a
nonpolar organic solvent in which the pigment
molecules are soluble. This mixture is then filtered
to remove all de
is. The biology lab technician
has already prepared the mixture for you. The
solvent is extremely flammable, so use caution in
handling both the pigment solution and the
solvent.
Record the abso
ance for the specific
wavelengths given in the Table 3. You should
cali
ate (blank) the spectrophotometer every time
you change the wavelengths. Note this data is
provided for you in Table 3.
Table 3: Absorption Spectrum Data fo
Spinach Chloroplast Extract
Wavelength Abso
ance Wavelength Abso
ance Wavelength Abso
ance
380 nm
0.725
500 nm
0.139
620 nm
0.100
400 nm
0.834
520 nm
0.074
640 nm
0.135
420 nm
0.971
540 nm
0.047
660 nm
0.406
440 nm
0.844
560 nm
0.041
680 nm
0.049
460 nm
0.678
580 nm
0.059
700 nm
0.029
480 nm
0.338
600 nm
0.079
720 nm
0.000
Using Excel make a graph of the abso
ance versus the
wavelength.
Underneath the graph in your Excel spreadsheet answe
these two questions:
My Blackboard Courses Community
Page 6 of 7
Table of Contents
Learning Objectives
Background Information
Photosynthesis Pre-lab Quiz
Effect of Light Intensity on the Rate of Photosynthesis
Separation of Chloroplast Pigments by Paper Chromotography
Absorption Spectrum of Chloroplast Extract
Photosynthesis La
Henry Tolbert
https:
-montgomerycollege.blackboard.com/webapps
lackboard/execute/courseMain?course_id=_90514_1
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2. Based on your observations, which wavelength
(color) of light might be expected to generate the
highest rate of photosynthesis? _________
3. Why are plants typically green?
4. Photosynthesis produces the oxygen (O ) on which
all aerobic organisms depend for survival. What
other factors make photosynthesis essential to the
maintenance of virtually all life on earth?
2
separation-of-chloroplast-pigments-by-paper-chromotography-22ulcswk.pdf
Week 9 Photosynthesis XXXXXXXXXXBIOL XXXXXXXXXXCourse Content Unit 3 - Weeks 9 - 12
Page 5 of 7
Separation of Chloroplast Pigments by Pape
Chromotography
1. molecular weight
2. solubility in the specific solvent
3. affinity for the pape
As was noted earlier, the primary
photosynthetic pigment is chlorophyll a;
however, other accessory pigments (e.g.,
xanthophylls and carotenes) are also
typically present in the chloroplast, albeit in
smaller quantities. There are several
techniques by which these primary and
accessory pigments can be separated. In
this exercise, the separation will be
accomplished by paper chromatography.
When a solution of these pigments is placed
on a strip of filter paper, the pigment
molecules adso
onto the cellulose fibers of
the paper. When the tip of the strip of pape
is then immersed into a suitable solvent, the
solvent is abso
ed by the paper and moves
up the paper by capillary action. As the
solvent passes the spot on which the
pigment solution was placed, the pigments
are dissolved by the moving solvent. The
pigment molecules are generally unable to
move as fast as the solvent, but some of
them move faster than others. The
differential movement of the pigments is
caused by three main factors that diffe
among the pigments:
Faster movement is associated with low
molecular weight, high solubility in the
solvent, and low affinity for the paper. The
distance traveled by a particular pigment
elative to the distance traveled by the
solvent is specific for any given pigment and
set of conditions. This relationship is called
the R , and is calculated as follows:f
The R for any given substance is constant
in a specific solvent separation system;
thus, it can be used to characterize the
pigment molecules.
f
Experimental Procedure for completing the wet-lab.
Please read so that you understand at what
steps the data was collected and what the
data represent.
Table 2: Photosynthetic Pigments
Separated by Paper Chromatography
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Page 5 of 7
Table of Contents
Learning Objectives
Background Information
Photosynthesis Pre-lab Quiz
Effect of Light Intensity on the Rate of Photosynthesis
Separation of Chloroplast Pigments by Paper Chromotography
Absorption Spectrum of Chloroplast Extract
Photosynthesis La
Henry Tolbert
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Substance that migrated Distance
from
the
origin
Rf
petroleum ether-acetone solvent 10.0 cm
photosynthetic
pigment
carotenes 9.3 cm
xanthophylls 4.3 cm
chlorophyll
a
5.3 cm
chlorophyll
1.3 cm
Put the above data and calculations for the
Rf on its own page of your Excel
spreadsheet and then answer the following
questions.
XXXXXXXXXXWhat can be deduced about a molecule that has a
very high Rf?
2. Which pigment in spinach leaves do you think is
most soluble in the petroleum ether-acetone solvent
we used in today’s lab?
3. What is the maximum value that the Rf can be fo
any molecule?
4. Would you expect the Rf of chlorophyll a to be the
same or different if the solvent were something
other than that used in this exercise? Explain why
or why not.
effect-of-light-intensity-on-the-rate-of-photosynthesis-ndash-ebekhy44.pdf
Week 9 Photosynthesis XXXXXXXXXXBIOL XXXXXXXXXXCourse Content Unit 3 - Weeks 9 - 12
Page 4 of 7
Effect of Light Intensity on the Rate of
Photosynthesis
One of the products of
photosynthesis is
molecular oxygen (O ).
Oxygen is only slightly
soluble in water, so in a
saturated solution, the
excess oxygen will form
gaseous bu
les. The
ate of oxygen
evolution by a plant
immersed in water can
e a reasonable
measure of the rate of
photosynthesis. We will
set up a system that
can measure the
amount of oxygen gas
eleased from plant
leaves. We will use the
system to determine
the effect of varying
light intensity (using
light bulbs of differing
wattage) on the rate of
photosynthesis.
2
My Blackboard Courses Community
Page 4 of 7
Table of Contents
Learning Objectives
Background Information
Photosynthesis Pre-lab Quiz
Effect of Light Intensity on the Rate of Photosynthesis
Separation of Chloroplast Pigments by Paper Chromotography
Absorption Spectrum of Chloroplast Extract
Photosynthesis La
Henry Tolbert
https:
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