Photosynthesis and pigments

1. CHLOROPHYLL
AND OTHER
PIGMENTS

3. BACKGROUND INFORMATION
Photosynthesis is the process
used by plants, algae and
certain bacteria to harness
energy from sunlight and turn it
into chemical energy.
Most living things depend on
photosynthetic cells to
manufacture the complex
organic molecules they
require as a source of
energy. Photosynthetic cells
are quite
diverse and include cells
found in green plants,
phytoplankton, and
cyanobacteria.

4. BACKGROUND INFORMATION
During the process of
photosynthesis, cells use
carbon dioxide and energy from
the Sun to make sugar
molecules and oxygen. These
sugar molecules are the basis
for more complex molecules
made by the photosynthetic
cell, such as glucose.
Then, via respiration
processes, cells use oxygen
and glucose to synthesize
energy-rich carrier
molecules, such as ATP, and
carbon dioxide is produced
as a waste product.
Therefore, the synthesis of
glucose and its breakdown
by cells are opposing
processes.

5. Photosynthesis takes place in two sequential stages:
1. The light-dependent reactions;
2. The light-independent reactions, or Calvin Cycle.

6. LIGHT-DEPENDENT REACTIONS
Just as the name implies, light-
dependent reactions require
sunlight. In the light-dependent
reactions, energy from sunlight
is absorbed by chlorophyll and
converted into stored chemical
energy,

7. LIGHT-DEPENDENT REACTIONS
in the form of the electron
carrier molecule NADPH
(nicotinamide adenine
dinucleotide phosphate) and the
energy currency molecule ATP
(adenosine triphosphate).
The light-dependent reactions
take place in the thylakoid
membranes in the granum
(stack of thylakoids), within the
chloroplast.

9. Figure: The two stages of
photosynthesis: Photosynthesis
takes place in two stages: light-
dependent reactions and the
Calvin cycle (light-independent
reactions).
Light-dependent reactions,
which take place in the
thylakoid membrane, use light
energy to make ATP and
NADPH. The Calvin cycle,
which takes place in the
stroma, uses energy derived
from these compounds to
make GA3P from CO2.

10. Photosystems are the functional
units for photosynthesis, defined by
a particular pigment organization
and association patterns, whose
work is the absorption and transfer
of light energy, which implies
transfer of electrons. Physically,
photosystems are found in the
thylakoid membranes.
PHOTOSYSTEMS

12. In the light-independent reactions
or Calvin cycle, the energized
electrons from the light-dependent
reactions provide the energy to
form carbohydrates from carbon
dioxide molecules. The light-
independent reactions are
sometimes called the Calvin cycle
because of the cyclical nature of
the process.
Although the light-independent
reactions do not use light as a
reactant (and as a result can
take place at day or night),
they require the products of
the light dependent reactions
to function.
LIGHT DEPENDENT REACTION

13. The light-independent molecules
depend on the energy carrier
molecules, ATP and NADPH, to
drive the construction of new
carbohydrate molecules. After the
energy is transferred, the energy
carrier molecules return to the
light-dependent reactions to obtain
more energized electrons. In
addition, several enzymes of the
light-independent reactions are
activated by light.

14. Chlorophyll is a green
photosynthetic pigment found in
plants, algae, and cyanobacteria.
Chlorophyll absorbs mostly in the
blue and to a lesser extent red
portions of the electromagnetic
spectrum, hence its intense green
color.
Green substance in producers
that traps light energy from the
sun, which is then used to
combine carbon dioxide and
water into sugars in the
process of photosynthesis
Chlorophyll is vital for
photosynthesis, which helps
plants get energy from light.
CHLOROPHYLL

15. Chlorophyll molecules are
specifically arranged in and
around pigment protein
complexes called
photosystems, which are
embedded in the thylakoid
membranes of
chloroplasts.
CHLOROPHYLL

16. There are four types of chlorophyll:
chlorophyll a, found in all higher
plants, algae and cyanobacteria;
chlorophyll b, found in higher
plants and green algae; chlorophyll
c, found in diatoms, dinoflagellates
and brown algae; and chlorophyll
d, found only in red algae.
In plants, chlorophyll a and
chlorophyll b have prominent
absorption roles as pigments.
Chlorophyll a and b differ in
structure and function. In
photosynthesis, chlorophyll a
plays a more important role
,as it is the one that directly
absorbs light energy.
CHLOROPHYLL PIGMENTS

17. In contrast , chlorophyll b is
considered an accessory pigment
because it transfers only the
absorbed light energy to
chlorophyll
a.
You see chlorophyll as green
because this is the only color
that most plants do not
absorb. Both chlorophyll a and
b absorb violet, blue, and red
lights, and they reflect the
green light back to our eyes
CHLOROPHYLL PIGMENTS

18. Carotenoid, another common
pigment, also plays an accessory
role. It is in the shade of yellow and
orange because again, these
colors are the ones that are
reflected back to our eyes.
It absorbs only the violet –
blue-green range. During
autumn in most temperate
regions, carotenoid pigments
become apparent in trees
because their chlorophyll
breaks down.
CHLOROPHYLL PIGMENTS

20. What Cells and
Organelles Are
Involved in
Photosynthesis?
Photosynthetic cells contain
special pigments that absorb
light energy. Different
pigments respond to different
wavelengths of visible light.
Chlorophyll, the primary
pigment used in
photosynthesis, reflects green
light and absorbs red and
blue light most strongly.

21. In plants, photosynthesis takes
place in chloroplasts, which
contain the chlorophyll.
Chloroplasts are surrounded by a
double membrane and
contain a third inner membrane,
called the thylakoid membrane that
forms long
folds within the organelle.
The green pigment chlorophyll
is located within the thylakoid
membrane, and the space
between the thylakoid and the
chloroplast membranes is
called the stroma .

22. Chlorophyll A is the major pigment
used in photosynthesis, but there
are several types of chlorophyll
and numerous other pigments that
respond to light, including red,
brown, and blue pigments.
These other pigments may
help channel light energy to
chlorophyll A or protect the cell
from photo-damage.

23. For example, the
photosynthetic protists called
dinoflagellates, which are
responsible for the "red tides"
that often prompt warnings
against eating shellfish,
contain a variety of light
sensitive pigments, including
both chlorophyll and the red
pigments responsible for
their dramatic coloration.