This document summarizes photosynthesis and its key stages and components. Photosynthesis occurs in chloroplasts in plant leaves and stems. It uses carbon dioxide, water, and sunlight to produce oxygen and energy in the form of ATP and NADPH. There are two stages - the light reactions where solar energy is converted to chemical energy, and the Calvin cycle where carbon is fixed into sugars. Chlorophyll is the pigment that absorbs sunlight. Photosystems and chloroplast membranes are involved in the light reactions. The Calvin cycle involves carbon fixation, reduction of 3-PGA into G3P using ATP and NADPH, and regeneration of RuBP to repeat the cycle and produce glucose. Photosynthesis is vital as it provides food

1. PHOTOSYNTHESIS
Christian Jay A. Mabitazan

2. introduction
Photosynthesis nourishes
almost the entire living world
directly or indirectly.
An organism acquires the
organic compounds it uses
for energy and carbon
skeletons by one of two
major modes: autotrophic
nutrition or heterotrophic
nutrition.
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4. Photosynthesis
o The conversion process
that transforms the
energy of sunlight into
chemical energy stored
in sugars and other
organic molecules.

5. Elysia cholorotica
Acyrthosiphon pisum
Ambystoma maculatum

6. Where does it take
place?
o In plants, photosynthesis
takes place in chloroplasts,
which contain the
chlorophyll.
o All green parts of a plant,
including green stems and
unripened fruit, have
chloroplasts, but the
leaves are the major sites
of photosynthesis in most
plants.

7. Chloroplasts
o A typical mesophyll cell
has about 30–40
chloroplasts.
o According to what has
come to be known as the
endosymbiont theory,
the original chloroplast
was a photosynthetic
prokaryote that lived
inside an ancestor of
eukaryotic cells.

9. Chloroplasts
o A chloroplast has two membranes
surrounding a dense fluid called
the stroma.
o Suspended within the stroma is a
third membrane system, made up
of sacs called thylakoids.
o In some places, thylakoid sacs are
stacked in columns called grana
(singular, granum). Chlorophyll,
the green pigment that gives
leaves their color, resides in the
thylakoid membranes of the
chloroplast.

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12. STAGES OF
PHOTOSYNTHESIS
• Light Reaction • Calvin Cycle (“Dark Reaction”)
The step of photosynthesis that convert
solar energy to chemical energy. Water
is split, providing a source of electrons and
protons (hydrogen ions, H+) and giving off
O2 as a by-product.
The light reactions use solar energy to
reduce NADP+ to NADPH by adding a
pair of electrons along with an H+. The
light reactions also generate ATP, using
chemiosmosis to power the addition of a
phosphate group to ADP, a process called
photophosphorylation.
Calvin cycle is also known as the C3 cycle
or the “dark reaction”. The Calvin cycle is
named for Melvin Calvin, who, along with
his colleagues James Bassham and
Andrew Benson, began to elucidate its
steps in the late 1940s.
It is the cycle of chemical reactions where
the carbon from the carbon cycle is fixed
into sugars.

14. Light Reactions
o It is the first stage of
photosynthesis in which
solar energy is converted
into chemical energy in the
form of ATP and NADPH.
o Water molecule is split up
and NADP+ is reduced to
NADPH, thus producing O2
molecule.

15. Chlorophyll
o Chlorophyll is a pigment that
gives plants their green color,
and it helps plants create
their own food through
photosynthesis.
o There are two known types of
chlorophyll: a and b.

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18. Photosystem
o Photosystems are structures
within the thylakoid
membrane that harvest light
and convert it to chemical
energy.
o A photosystem is composed
of a reaction-center complex
surrounded by several light-
harvesting complexes.

19. Photosystem
o The reaction-center chlorophyll
a of photosystem II is known
as P680 because this pigment is
best at absorbing light having a
wavelength of 680 nm (in the
red part of the spectrum).
o The chlorophyll a at the
reaction-center complex of
photosystem I is called P700
because it most effectively
absorbs light of wavelength 700
nm (in the far-red part of the
spectrum).

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24. Calvin Cycle
o It is anabolic, building carbohydrates from smaller molecules and
consuming energy.
o Carbon enters the Calvin cycle in the form of CO2 and leaves in the form of
sugar. The cycle spends ATP as an energy source and consumes NADPH as
reducing power for adding high-energy electrons to make the sugar.

25. Stages of Calvin Cycle
o Carbon Fixation: A CO2 molecule combines with a five-carbon
acceptor molecule, ribulose-1,5-bisphosphate (RuBP). This step
makes a six-carbon compound that splits into two molecules of a
three-carbon compound, 3-phosphoglyceric acid (3-PGA). This
reaction is catalyzed by the enzyme RuBP carboxylase/oxygenase,
or rubisco.
o Reduction: ATP and NADPH are used to convert the 3-PGA
molecules into molecules of a three-carbon sugar, glyceraldehyde-3-
phosphate (G3P).
o Regeneration. Some G3P molecules go to make glucose, while
recycled to regenerate the RuBP acceptor.

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27. Light reactions produce NADPH, ATP,
and oxygen that we breathe, while
Calvin Cycle processes carbon dioxide
to become glucose that makes up our
food and energy.
Photosynthesis is an intricate chemical
process which involves fairly simple
reactants, but gives out profound
products. It is a process not only vital to
plants, but to all of us.Without it,
possibility of life on Earth will be in
question.
summary

28. THANKYOU!
Christian JayA. Mabitazan
cjmabitazan9297@student.dmmmsu.edu.ph