Lesson 8.
Photosynthesis and the
Role of Pigments
General Biology 11/2
Science, Technology, Engineering, and Mathematics
Inside our home, some
of us love the kitchen
the most.
The kitchen is where
most of the food are
prepared.
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We all know that plants make their
own food as well, but through the
use of sunlight.
How is this possible?
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Pigments in plants do not just serve the purpose of giving vivid
colors. They have their own importance related to food
production.
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Learning Competency
At the end of the lesson, you should be able to do the following:
Explain the importance of chlorophyll and other
pigments (STEM_BIO11/12-IIa-j-3).
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Learning Objectives
At the end of the lesson, you should be able to do the following:
● Explain the functions of photosynthetic pigments.
● Distinguish principal photosynthetic pigments
from accessory photosynthetic pigments.
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Photosynthetic Pigments
● Autotrophs produce
their own food by
harnessing the energy
from the sun.
○ They perform this
in their
chloroplasts.
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Photosynthetic Pigments
The characteristic color of plants allows them to become the primary producers
in ecosystems by harnessing solar energy to produce high-energy organic
molecules. 8
Photosynthetic Pigments
Pigments
● organic molecules
● selectively absorb light
of specific wavelengths
● built in the thylakoid
membranes
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Photosynthetic Pigments
Wavelength of Light
● Wavelengths of light
that are not absorbed
are reflected.
● Reflected light gives
each pigment its
characteristic color.
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Photosynthetic Pigments
For instance, a red apple can be perceived as red because the pigments in the
apple’s skin absorb the other colors, leaving only the red portion of the spectrum
to be reflected. The photoreceptors of our eyes then detect these reflected
colors. 11
Photosynthetic Pigments
Variegation in the leaves of some plants reduces their capacity for
photosynthetic activity. However, in the wild, this results in an advantage that
they become less likely eaten by herbivores. 12
Principal Pigment
Chlorophyll a
● site for photosynthesis
● found in the chloroplast
● converts solar energy to
chemical energy
● consists of a porphyrin
ring with a central
The chloroplast is a cell organelle in most
autotrophs that can convert solar energy magnesium core
into reusable chemical energy. 13
Principal Pigment
The structure of chlorophyll a is similar to the other type of chlorophyll, the
chlorophyll b. They differ in only one functional group (in red), CHO being
present in chl b. 14
Accessory Pigments
Chlorophyll b
● absorbs mainly blue and
orange light but reflects
olive green
● does not participate
directly in light reactions
The chloroplast is a cell organelle in most
autotrophs that can convert solar energy
into reusable chemical energy. 15
Accessory Pigments
The molecular structure of chlorophyll b (left) is very much like that of the
chlorophyll a. They differ in only one functional group, with a methyl group
present in chlorophyll a and aldehyde group in chlorophyll b. 16
Accessory Pigments
Chlorophyll b
● present only in green
algae and higher plants
● breaks down faster than
the other pigments
Chlorophyll b is also present in higher
plants and green algae, such as Volvox. 17
Accessory Pigments
Accessory pigments chlorophyll c and d are present in brown algae (left,
Sargassum sp.) and red algae (right, Gracilaria sp.), respectively.
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Accessory Pigments
Carotenoids
● various shades of red,
yellow, and orange
● absorbs mainly violet,
blue, and green light
● appear once the
chlorophyll breaks down
Carotenoids are evident in autumn leaves in
temperate regions. 19
Accessory Pigments
Carotenoids
● divided into carotenes
and xanthophylls
● Carotenes include alpha-
carotene, beta-carotene,
and lycopene
● Xanthophyll includes
lutein and fucoxanthin
Carotenoids are evident in many of our
fruits and vegetables, such as ripe bell
peppers. 20
Accessory Pigments
Phycobilins
● found in red algae and
cyanobacteria
● water-soluble, present
in the aqueous
cytoplasm or stroma of
Aside from chlorophyll a, the prokaryotic chloroplasts
and “alga-like” cyanobacteria also have
phycobilins that aids them during
photosynthesis. 21
Let’s Sum It Up!
● Photosynthesis is the process in which plants
harness solar energy and use it to synthesize high-
energy organic compounds in the form of sugars.
● The process of photosynthesis in plants and algae
occurs in the membrane-bound organelle called
chloroplasts.
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Let’s Sum It Up!
● Pigments are organic molecules that selectively
absorb light of specific wavelengths and are built
into the thylakoid membranes of the chloroplasts.
● Photosynthetic pigments can be classified into
primary and accessory pigments based on their
contribution to light energy harvesting during
photosynthesis.
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Let’s Sum It Up!
● Chlorophyll a is the primary pigment during
photosynthesis. It is also the universal pigment in all
photosynthetic organisms. It participates directly in
light reactions and is the most common green
photosynthetic pigment in plants, algae, some
protists, and cyanobacteria. This pigment absorbs
mainly blue, violet, and red light, thus it appears
green to us.
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Let’s Sum It Up!
● Chlorophyll b, an accessory pigment, absorbs
mainly blue and orange light but reflects olive
green. Although chlorophyll b does not participate
directly in light reactions, it conveys absorbed
energy to chlorophyll a to work in the light
reactions.
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Let’s Sum It Up!
● Other types of chlorophyll exist, particularly
chlorophylls c and d. These accessory pigments are
found in brown and red algae, respectively.
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Let’s Sum It Up!
● Carotenoids are accessory pigments consisting of
various shades of yellow and orange. These
pigments absorb mainly violet, blue, and green light.
This pigment is important in photoprotection.
These pigments also convey light energy harvest
from other bands of the visible light from the sun.
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Let’s Sum It Up!
● Phycobilins are also accessory pigments in red
algae and cyanobacteria that either give red or blue
coloration. They are especially important for deep-
sea red algae as they can utilize the blue light that
can penetrate into deeper waters.
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Let’s Sum It Up!
Aside from the primary and accessory classification of
photosynthetic pigments, they can also be classified into
chlorophyll, carotenoids, and phycobilins. 29
