Cyclic and non-cyclic photophosphorylation are two types of photophosphorylation involved in photosynthesis. Non-cyclic photophosphorylation involves both photosystem I and II and uses electrons from the splitting of water, producing oxygen as a byproduct. Cyclic photophosphorylation only involves photosystem I and cycles electrons back without splitting water or producing oxygen. Both mechanisms use the electron transport chain to produce ATP, but only non-cyclic photophosphorylation produces NADPH in addition to ATP.

1. Cyclic And Non-Cyclic
Photophosphorilation
BIOSCIENCE FOR NANOTECHNOLOGY

2. OVERVIEW OF
PHOTOSYNTHESIS
A process by which autotrophic
organisms use light energy
(sunlight) to make sugar & oxygen
gas from carbon dioxide & water.

3. light
oxygen
carbon
dioxide
carbohydrates
water

4. PHOTOSYNTHESIS PROCESS
LIGHT REACTIONS DARK REACTIONS
No light needed. Instead, dark
reactions use ATP and NADPH to
produce energy molecule.
Light needed to produce organic
energy molecules ATP and NADPH.

5. PHOTOPHOSPHORYLATION
The synthesis of ATP from ADP and
inorganic phosphate in presence of
light is known as photophosphorylation.

6. TYPES OF PHOTOPHOSPHORYLATION
NON – CYCLIC
PHOTOPHOSPHORYLATION
CYCLIC
PHOTOPHOSPHORYLATION
01 02

7. PIGMENTS INVOLVED
•There are many pigments involved –
 Chlorophyll - Chlorophyll a, b, c, d,
Bacteroid chlorophyll, Bacterioviridin.
 Carotenoids - Xanthophylls and
Carotene.
 Phycobilin – Phycocyanin and
Phycoerythrin
•Chlorophyll a = reaction centre
•Other pigments = Accessory pigments

8. SITE OF PHOTOSYNTHESIS
 Chloroplast - found in mesophyll cells of leaves
 The photosynthesis takes place in chloroplast.
 Chlorophyll pigments are present in thylakoids.
 The thylakoids are arranged in stacks like the
piles of coins called grana
 Stroma lamellae connect granum to each other
and also to inner membrane of chloroplast.
 The cytoplasm of the chloroplast is called stroma.
 The stroma of the chloroplast contains enzymes
required for the synthesis of carbohydrates and
proteins.

9. Photosystem
 Photosystems are pigments that are organized in
the thylakoid membrane in to two different
photosystems (PS I & PS II)
 Each PS has one specific chlorophyll – a, and many
other accessory pigments bound by proteins.
 Chlorophyll – a forms the reaction center (actual
reaction takes place) other pigments form the light
harvesting complex (LHC) called antennae which
gather light and transfer it to reaction center.
 PS I reaction center is P700 (chlorophyll –a absorbs
light at 700 nm)
 PS II reaction center is P680 (chlorophyll –a absorbs
light at 680 nm)

10. PHOTOPHOSPHORYLATION
NON-CYCLIC

11. NON – CYCLIC PHOTOPHOSPHORYLATION

12. NON- CYCLIC PHOTOPHOSPHORYLATION
 Plants and cyanobacteria utilize two
photosystems which work sequentially to
produce both energy and reducing power.
 First, a photon of light ejects a high electron
from photosystem II.
 The electron lost from photosystem II does
not return to photosystem II, but is replaced
by an electron generated from the
enzymatic splitting of water and the release
of oxygen.
 The electron then travels from the excited
reaction center of photosystem II down an
electron transport chain and finally to the
reaction center of photosystem I.
 This transport system produces ATP.
 Since the excited electron does not return
to photosystem II, this mechanism for
making ATP is called non-cyclic
photophosphorylation.
 OVERALL RESULT OF Z-SCHEME.
 The result of the non-cyclic electron flow is
that water is oxidized yielding H+, e- and O2.
 ATP is produced.
 NADP+ becomes NADPH2.
 The hydrogen and Energy of NADPH2 and
ATP produced in the light reaction are used
in dark reaction.
 PQ - Plastoquinone
 PC - Plastocyanin

13. PHOTOPHOSPHORYLATION
CYCLIC

14. CYCLIC PHOTOPHOSPHORYLATION

15. CYCLIC
 When an electron is energized by absorption of
light, it is ejected from the photosystem
reaction center.
 The electron then passes down through an
electron transport system, and finally to the
reaction center.
 The energy released during this electron
transport is used to produce ATP.
 Since the excited electron returns to the
reaction center, this mechanism for making
ATP is called cyclic photophosphorylation.
PHOTOPHOSPHORYLATION

16. PHOTOSYSTEM I PHOTOSYSTEM II
Reaction center
P700 Chlorophyll a
(absorb 700nm)
P680 Chlorophyll a
(absorb 680nm)
Cycling
Involves in both cyclic
and non-cyclic
photophosphorylation
Involved only in non-
cyclic
photophosphorylation
Location
Non-cyclic: Outer surface
of thylakoid membrane
Cyclic: stroma lamellae
Inner surface of thylakoid
membrane
Photolysis Of
Water
Does not occur Occur
Oxygen
Production
Does not occur Occur
Formation Of
NADPH
Occur Does not occur
Source Of
Electron
Non-cyclic: PS II
Cyclic: Chlorophyll a
From photolysis of water

17. Non-cyclic Photophosphorylation Cyclic Photophosphorylation
It is associated with both PS I and PS II. It is associated with PS I.
The electrons are not cycled back but
compensated by the electrons from
photolysis of water.
The electron expelled from chlorophyll
molecule is cycled back.
Photolysis of water and evolution of
oxygen (byproduct) take place.
Photolysis of water and evolution of
oxygen (byproduct) do not take place.
Photophosphorylation takes place only
at one place.
Photophosphorylation takes place at
two places.
NADP+ is reduced to NADPH2. NADP+ is not reduced.
ATP and NADPH2 is synthesized. Only ATP is synthesized.
H2O is external source of electron.
No external source of electron is
needed.

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