Plant Pigment/ Paper Chromatography Lab
Laiba Sairah Ninan
Partner: Brendan Lathrop
AP Biology
Ms. Ranney
Period 1, 2
I.
Title:
Plant Pigment/ Photosynthesis Lab
II.
Purpose: The purpose of the lab is to separate plant pigments using
chromatography.
III. Procedures:
1. Cut chromatography paper strip. Use scissors to cut off the two bottom of the
strip.
2. Measure 2 cm from the bottom of the paper strip.
3. Lightly draw a pencil line across the strip.
4. Place the leaf over the pencil line and roll a quarter over the line.
5. Repeat until there is a very dark green line over the pencil line at least 15 times.
6. Place 1 cm of solvent in a graduated cylinder.
7. Slowly lower the chromatography paper into flask. Do not allow pigment to
touch solvent.
8. Let solvent rise until it reaches the mark at top of paper.
9. Stop just before solvent front reaches top.
10. Remove chromatography paper and immediately draw a pencil line across the
top of the strip where the solvent front got to before it dries.
11. Draw a pencil line at the top of each pigment, showing how far that pigment
traveled.
IV. Observations/Data:
Band Number
Name of
Pigment
Solvent
N/A
1 (top)
Xanthophyll
2
Carotene
3
4 (bottom)
V.
Chlorophyll A
Chlorophyll B
Color of
Pigment
Yellow
Yellow orange
Green
Gray – green
Migration
Distance (mm)
66
66
9
Rf value
6
2
.09
.03
1.0
1.0
.14
Discussions/Analysis: I have edited this to show you how to turn the questions
into a good discussion/analysis paragraph.
The factors that are involved in the separation of the pigments in this lab are
solubility, size of particles, and their attractiveness to the paper are involved in
the separation of the pigments. Beta Carotene was the lightest molecular weight
and does not contain any available oxygens to form hydrogen bonds with the
paper. Therefore it stayed with the solvent front and traveled up the paper the
furthest. Conversely chlorophyll molecules were heavier moleclular weight and
formed hydrogen bonds with the paper and so did not travel as far on the paper.
The Rf values for the pigments that were measured during this lab were unique
to the solvent used (a chromatography mixture of acetone and alcohol provided
by Carolina Biological). However, the magnitude of the values will be relative to
each other so the order of pigments (least soluble, slowest moving to most
soluble, fasting moving will be the same
Chlorophyll a, being the main photosynthetic pigment, has a primary purpose to
convert light energy to chemical energy used by the plant itself. Chlorophyll b
absorbs light in a region of the spectrum apart from the dominant chlorophyll,
and transfers the energy it produces to chlorophyll a. Along with chlorophyll b in
transferring their energy produced to the dominant chlorophyll, two other
pigments that are found in plants are carotenes and xanthophylls, which are
orange and yellow respectively. Since chlorophyll is such a dominant pigment in
green plants, this domination hides the color of the carotenes and xanthophylls in
the leaves.
The pigment that traveled the furthest was carotene because it was the most
soluble in the solvent. Chlorophyll b traveled least because it was the least
soluble in the solvent.
The pigment inside the leaf absorbs all colors except the one shown. If a leaf is
green then it absorbed all colors except green. This lab showed that there was
much more green pigments (cholorophyll a and b) than yellow pigments because
the green bands were the darkest and thickest on the paper. That is why spinach
leaves are green.
1. ?
We could use the same paper chromatography experiment performed for this lab
to determine if a different plant had the same pigments. We could compare the
Rf values from the spinach leaf to the Rf values from those of the different plant
to determine if they had the same pigments. In autumn, chlorophyll starts to
break down which allows the other brilliant plant pigment colors to show. These
pigments include the red, orange, and yellow colors.
By spraying the leaf, yellow, a light pigment that is not used by the plant in
photosynthesis, Abby and Melissa did not interfere with photosynthesis that was
occurring naturally in the plant because the plant was still able to receive and
absorb red and blue lights. Conversely it appears that the light paint coating may
have helped the plant by insulating the leaf from the decreased temperature of
the fall so that the enzymes that are involved in photosynthesis could continue
working after those in the leaves that were green stoped.
VI. Conclusion:
Paper chromatography proved to be an successful method of separating and
observing the various colors of plant pigments. The pigments dissolved in the
solvent and migrated upward. The colors were observed and their migration
distances were measured & recorded. The Rf value of each pigment was determined
by dividing its migration by the migration of the solvent. It was determined that 4
pigments were present in the original spot --- carotene, xanthophyll, chlorophyll a,
and chlorophyll b. Carotenewas the most soluble, while chlorophyll b was the least
soluble.