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Photosynthesis Absorption and Conversion of Energy
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Autotrophs
An autotroph is an organism that can make its own
food through.
auto self
troph organism
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All organisms must break down carbohydrates, or
other complex molecules, to form energy
molecules, such as Adenosine Triphosphate (ATP).
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Illustration by PROF. K.SEDDON DR.
T.EVANS, QUEEN'S UNIVERSITY BELFAST
The chemical formula of ATP is C10H16 N5O16P3.
ATP. Computer artwork of a molecule of adenosine
triphosphate (ATP), which is a carrier of
metabolic energy in the cell. Energy is stored in
the chemical bonds and is released when the
molecule is broken down.
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1.       Light is the purest form of energy and
the prime source of energy of all life.
a. provides energy for photosynthesis
b. visible spectrum array of colors formed
when white light passes through a prism
c. photons unit of light energy
d. color of an object seen by the eye is the
color of light reflected by the object
Photograph by Stanley Mikles, September 2006,
West of Emily Minnesota
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Photo by Dr Tim Evans
2. Chlorophyll
a. found in chloroplasts (in Eukaryotes) 1) pla
nts 2) some algae
b. found in cytoplasm of prokaryotes
c. necessary for photosynthesis to begin
d. absorbs energy from all but the green
portion of the visible spectrum
e. several types of chlorophylls are active
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f. acts as a light (energy) trap during
photosynthesis
1) when a photon strikes a chlorophyll molecule
and is absorbed, the photons energy is
transferred to an electron of the chlorophyll
molecule
2) The energized electrons are stretched like
rubber bands but they cannot remain for long
in this excited state
a) raised to a higher energy level
b) as electron returns to original level,
it releases absorbed energy
c) this energy is used in chemical reactions
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3. Other pigments are involved
a. xanthophylls yellow pigments that absorb
light energy in other parts of the spectrum and
pass the energy on to chlorophyll
b. carotene orange pigments
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4. Chloroplast plastid that stores chlorophyll
(plastid sack)
BIOPHOTO ASSOCIATES
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a. photosynthesis begins in thylakoid membrane
of a granum
b. stroma dense fluid that fills the space
between the grana and the chloroplastic membrane
PROF. KENNETH R. MILLER
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DR KARI LOUNATMAA
Pisum sativum
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Starch Grain
Pisum sativum
DR JEREMY BURGESS
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Coleus blumei
Starch Grain
DR JEREMY BURGESS
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The Origin of Chloroplasts?
Chloroplast Dividing
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Photosynthesis occurs in two phases.
I. Light-Dependent Reactions
Trapping of light energy and formation of
materials needed in the next phase.
A. light energy photon packet of light
energy
1) c 3.0 x 108 meters/second 186,000 mile/sec
2) Emc2
3) Mass of photon _at_ less than mass
of electron (9.0 x 10-31kg)
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B. chlorophyll molecules in
thylakoid membranes (grana) of chloroplast
struck by photon
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C. Chlorophyll molecular bonds broken releasing
energy (excited electrons)
1. Excited electrons move down electron
transport chain.
a. Embedded In the thylakoid membrane are a
series of proteins whose electrons are very
excitable.
b. The excited electrons move from protein to
protein in the thylakoid.
c. At each protein, the electrons lose energy.
d. Some of the energy lost at each step is
used to combine ADP and loose phosphate ions
(P) to form ATP.
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e. Some of the energy lost at each step is used
to split water molecules through a process
called hydrophotolysis. H2O H2 O
1) H used in next phase
First Photo System
2) O O O2 O2 diffuses out of
chloroplast into cytoplasm, diffuses out of
cell and into intercellular space, diffuses to
stomata, and is released by transpiration into
the atmosphere.
This is the source of 98 of all the free,
molecular oxygen in our atmosphere.
Open Stomata
Photo by DR JEREMY BURGESS
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Joseph Priestley (1733-1804
1. British chemist.
2. Best known as the discoverer of oxygen.
3. Carried out research into the composition
and nature of air.
4. First person to recognize that respiration in
animals produces carbon dioxide whereas in
plants it produces oxygen.
5. In his work on carbon dioxide, Priestley
invented soda water the precursor to all
carbonated drinks.
6. He was a Unitarian Calvinist minister and a
supporter of the French Revolution. Eventually
his political views led to his house being burnt
down and him fleeing England.
GEORGE BERNARD
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SCIENCE PHOTO LIBRARYJoseph Priestley. This
cartoon, of 1791 portrays Priestley, who
supported the French revolution, as a political
agitator. Priestley isolated and examined many
new gases including hydrogen chloride, nitrous
oxide, ammonia, nitrogen and carbon monoxide. He
was also the first to isolate oxygen but did not
correctly recognize its role in combustion,
believing instead that it played a part in the
'phlogiston' (combustible element)
theory. Priestley was persecuted for
his religious and political beliefs. He left
England in 1794.
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f. second photo system and a second electron
transport chain
g. The lost energy at each protein jump is
used to bond NADP to H.
h. The energy is also used to transport the
NADPH into the stroma by active transport.
i. NADPH is used in the light independent
reactions.
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• Light Independent Reactions
• (aka Dark Reactions, Dark Phase, Calvin Cycle)

A. Energy stored in ATP (ADP P
ATP) used as energy source in Light
Independent Reactions.
B. CO2 from atmosphere supplies carbon and
oxygen atoms for glucose. (C6H12O6)
C. NADPH from light dependent reactions used a
source of hydrogen used in glucose.
D. Occurs in the stroma of the chloroplast
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D. Light Independent Reactions (Calvin Cycle)
1. Carbon Fixation
One molecule of CO2 is added to one molecule
of RuBP (ribulose biphosphate), forming one
unstable six carbon molecule.
2. Formation of two 3 carbon
molecules. The unstable 6 carbon molecule
immediately breaks down into 2 3carbon
molecules of PGA.
3. Conversion of PGA to PGAL
a. One molecule of ATP broken into ADP
and P
b. One NADPH broken into NAPD- and H
c. Energy from ATP and NADPH forms the two
PGA into 2 PGAL (phosphoglyceraldehyde).
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Melvin Calvin
LAWRENCE, BERKELEY NATIONAL LABORATORY
1941
Photographed in 1961.
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1.          3. Reactions in the Calvin
Cycle a. Co2 and a 5-carbon molecule (RuBP)
combine to form a 6-carbon molecule (unstab
le intermediate) carbon fixation b. H2O
6 carbon molecule ? 2, 3-carbon molecules
(2PGA) c. 1 ATP molecule broken--energy used
to d. NADPH H ? NADP H2 e. Result 2,
3-carbon sugars (2PGAL) PGAL
Phosphoglyceraldehyde f. 1PGAL ? 6 carbon
sugar (glucose C6H12O6) g. 1PGAL returns
to beginning of cycle h. ATP split ATP ? ADP
P energy i. Yields return of 5-carbon
molecule RuBP from 1PGAL (back to start)  
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III. Synthesis without sunlight Chemosynthesis
(bacteria)
1. methane producers
2. Chemoautotrophs
3. digestive tracts
4. break down of sewage
5. break down of oil spills
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Stephen Hales
(1677-1761) English chemist and physiologist. His
book Vegetable Staticks (1727) describes 124
experiments on gases, which he made in several
ways and collected using a pneumatic trough. He
measured growth rates in plants, and showed that
light is needed, and that water loss (by
transpiration) is through the leaves and that
this causes an upward flow of sap. Later
experimented on blood pressure in animals and
investigated the vascular system in
general. Other studies involved the Preservation
of foods, water purification, the ventilation
of buildings and ships, and also the best way to
support pie crusts.
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Melvin Calvin
LAWRENCE, BERKELEY NATIONAL LABORATORY
1941
Photographed in 1961.
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Melvin Calvin. (born 1911), Portraits show Melvin
Calvin, an American biochemist, in his
photosynthesis research laboratory.
He began to study photosynthesis in 1946 when
sensitive analytical methods became available.
He identified in single-celled Chlorella algae a
cycle of photosynthetic reactions using
radioactive forms of carbon dioxide.
Photosynthesis is the process by which green
plants convert light, water carbon dioxide into
food and oxygen.
The discovery of this reductive pentose phosphate
or Calvin cycle, which occurs in all
photosynthesizing organisms, won Calvin the 1961
Nobel Chemistry Prize.