What Is the Role of Pigments in
Photosynthesis?
Light and Pigments
Role of Pigments
Pigments are light-absorbing colored molecules.
 Different pigments absorb different wavelengths
of light. Chlorophylls are the major lightabsorbing pigments in plants.
 They absorb energy from violet-blue light and
reflect green light, giving plants their green color.

Chloroplast
Accessory Pigments
 Role of Accessory Pigments:
 Accessory pigments help plants absorb
additional light. Plants need to make
these accessory pigments to maximize
the amount of photosynthesis they can
do.
 More pigments = More glucose or food
for the plant!
Types of Accessory
Pigments
Carotenoids: reflect yellow, orange, and red light.
 Carotenoids give carrots and sweet potatoes their
orange color and are very common in our area.
 Anthocyans: reflect red, blue, violet light.
 Xanthophylls: reflect yellow light.

Accessory Pigments
 Accessory pigments are the reason leaves
change colors in autumn. In green leaves,
there is so much chlorophyll that it masks the
other pigments.
 In autumn, as trees prepare to lose their
leaves, the chlorophyll molecules break
down, revealing the colors of other pigments.
The colors red, yellow, and orange can be
seen.
Chlorophyll a and b
http://file.scirp.org/Html/4-1190315%5C8cdaa9b5-1607-4e22bf41-2766e06060c9.jpg
Absorption Spectrum
http://www.emeraldecocity.com/clip_image002_0009.jpg
Differences in chlorophyll
Chlorophyll a will absorb light at
665 and 465 nm


Chlorophyll b will absorb light at 640
and 450 nm
Chlorophyll a has a CH3 group
Chlorophyll b has a C=OH group

(wider range of light absorbed=many plants are
green)
Uses for Chromatography

•
Chromatography is used by scientists to:
Analyze – examine a mixture, its components,
and their relations to one another
•
Identify – determine the identity of a mixture
or components based on known components
•
Purify – separate components in order to
isolate
one of interest for further study
•
Quantify – determine the amount of the a
mixture and/or the components present in the
sample
How does chromatography
work?

Solubility of molecule in solvent
used (better solubility further it will move)

Size of molecule (bigger, slower)

Attraction to the paper

Longer time, better separation
Purpose:
Do green leaves contain other
pigments?
1.Obtain a strip of chromatography paper.
2. Use a ruler to measure and draw a light pencil
line 2-cm above the bottom of the paper strip.
3. Place the edge of the spinach leaf over the
pencil line and using the edge of a coin gently
press on the spinach leaf to create a single green
line over the pencil line. You want this line to be
thin and concentrated with the pigment from the
spinach leaf. Therefore, repeat this edging process
carefully about 3-4 times. Be sure not to press too
hard or you will poke a hole
through the paper.
4. Carefully add isopropyl alcohol to the beaker
until it reaches a depth of 1-cm in the beaker.
5.Fold the top of the paper strip so that the
end of the strip with the green line hangs
down. The paper should be folded over the top
of the beaker with the bottom of the paper
strip just touching the alcohol. DO NOT have
alcohol touch spinach line
6. Record observations in data table.
Results:
Each pigment has an Rf value, the speed at which it moves
over the paper compared with the speed of the solvent.
Rf = Distance moved by the pigment
Distance moved by the solvent


Measure the distance in cm from the starting point (pencil
line) to the center of each pigment band. Then measure
the entire distance traveled by the solvent. Remember, the
starting point for the solvent is also the pencil line and the
ending point for the solvent is the top edge of the paper.
Do the required divisions and record your Rf values in the
DATA TABLE of your report sheet.
Images:
http://www.chs.helena.k12.mt.us/faculty/hbosch/biologytopics_file
s/webnotes/ch%208%20and%209/Ch8and9review_files/image002.
jpg
http://mrhalverson.com/2010B_chromatogram.png
Rf results:
Carotene: 1
Xanthophyll: 0.615
chlorophyll a:0.340
Chlorophyll b: 0.231