Photosynthesis Overview
CO2 + H2O

light

C6H12O6 + O2

photosynthesis – creating using light
Only chloroplast organelles ...
Photosynthesis: Two Major Processes
1.

The Light Reactions

 harvest light energy to

create ATP
2.

Calvin cycle

 Pro...
Photosynthesis
Light Reactions
Chloroplast Structure
The Light Reactions
1.

Photoexcitation

 Absorption of light

photons
2.

Electron transport

 Similar to ETC in

mitoc...
Photoexcitation
e- gain energy when
atoms absorb energy.
e- fall back to lowest
energy level (ground
state) if it isn’t
tr...
Light Absorbing Pigments
chlorophyll – groups of
light absorbing
molecules in green
plants
Chlorophyll Absorption Spectrum
Other Light Absorbing Pigments
carotenoids – other pigment molecules that can collect
light energy
Photosystems
chlorophyll and
other light
absorbing
pigments in the
thylakoid make
up a photosystem
protein
Photosystem Structure
reaction centre - the
chlorophyll a
molecule which the
light energy is
focused in a
photosystem

ele...
Photosystems
Two purposes:
1. to collect as much light energy as possible

2. excite chlorophyll a and transfer its electr...
Electron Transport
Electron transport occurs in the thylakoid membrane.
Two mechanisms of electron transport:
1. Non-cycli...
Thylakoid Membrane Proteins
Thylakoid Proteins: PSII
2e- transferred from H2O to
photosystem II (PS II)

also known as P680
(maximum absorption at
680...
Thylakoid Proteins: Pq
e- transferred to
plastiquinone (Pq) only
when enough energy is
collected by PSII

Pq is a mobile c...
Thylakoid Proteins: Cytochrome Complex
e- transferred from Pq to
cytochrome complex
protons pumped from
stroma to lumen ac...
Thylakoid Proteins: Pc
e- transferred to
plastocyanin (Pc)
Pc is a movable
component on thylakoid
surface in lumen
Thylakoid Proteins: PSI
e- transferred to
photosystem I (PSI)
also known as P700
(maximum absorption at
700 nm wavelength)
Thylakoid Proteins: Fd
e- transferred to
ferrodoxin (Fd) only
when enough energy
has been collected by
PSI

movable compon...
Thylakoid Proteins: NADP+ Reductase
e- transferred to
NADP+ reductase
final electron acceptor
is NADP+ that is
reduced to ...
NADP+ / NADPH

NAD+

NADP+
Thylakoid Proteins: ATP Synthase
protons pumped into the
lumen pass through
ATP synthase
ATP produced in stroma
photophosp...
Thylakoid Membrane Proteins
Non-cyclic Electron Flow: Z-Scheme
Non-cyclic Electron Transfer Summary
1. H2O is split to produce O2 (released from cell) and

H+ ions (released into lumen)...
Light Reaction Animation
Animation Link
Cyclic Electron Flow
Cyclic Electron Transfer Summary
1. only involves photosystem I (P700)
2. ferrodoxin returns electrons back to cytochrome
...
Tang 06  photosynthesis
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Tang 06 photosynthesis

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Tang 06 photosynthesis

  1. 1. Photosynthesis Overview CO2 + H2O light C6H12O6 + O2 photosynthesis – creating using light Only chloroplast organelles and special bacteria have the proteins necessary to carry out this function.
  2. 2. Photosynthesis: Two Major Processes 1. The Light Reactions  harvest light energy to create ATP 2. Calvin cycle  Process of producing C6H12O6 from CO2 and H2O
  3. 3. Photosynthesis
  4. 4. Light Reactions
  5. 5. Chloroplast Structure
  6. 6. The Light Reactions 1. Photoexcitation  Absorption of light photons 2. Electron transport  Similar to ETC in mitochondria 3. Photophosphorylation (chemiosmosis)  ATP synthesis due to electrochemical gradient
  7. 7. Photoexcitation e- gain energy when atoms absorb energy. e- fall back to lowest energy level (ground state) if it isn’t transferred to another molecule
  8. 8. Light Absorbing Pigments chlorophyll – groups of light absorbing molecules in green plants
  9. 9. Chlorophyll Absorption Spectrum
  10. 10. Other Light Absorbing Pigments carotenoids – other pigment molecules that can collect light energy
  11. 11. Photosystems chlorophyll and other light absorbing pigments in the thylakoid make up a photosystem protein
  12. 12. Photosystem Structure reaction centre - the chlorophyll a molecule which the light energy is focused in a photosystem electron acceptor
  13. 13. Photosystems Two purposes: 1. to collect as much light energy as possible 2. excite chlorophyll a and transfer its electrons to an electron acceptor and through a series of proteins (electron transport)
  14. 14. Electron Transport Electron transport occurs in the thylakoid membrane. Two mechanisms of electron transport: 1. Non-cyclic electron flow 2. Cyclic electron flow
  15. 15. Thylakoid Membrane Proteins
  16. 16. Thylakoid Proteins: PSII 2e- transferred from H2O to photosystem II (PS II) also known as P680 (maximum absorption at 680nm wavelength) light energy is required to help create O2 protons are released into the lumen
  17. 17. Thylakoid Proteins: Pq e- transferred to plastiquinone (Pq) only when enough energy is collected by PSII Pq is a mobile component within the thylakoid membrane
  18. 18. Thylakoid Proteins: Cytochrome Complex e- transferred from Pq to cytochrome complex protons pumped from stroma to lumen across thylakoid membrane
  19. 19. Thylakoid Proteins: Pc e- transferred to plastocyanin (Pc) Pc is a movable component on thylakoid surface in lumen
  20. 20. Thylakoid Proteins: PSI e- transferred to photosystem I (PSI) also known as P700 (maximum absorption at 700 nm wavelength)
  21. 21. Thylakoid Proteins: Fd e- transferred to ferrodoxin (Fd) only when enough energy has been collected by PSI movable component on thylakoid surface in stroma
  22. 22. Thylakoid Proteins: NADP+ Reductase e- transferred to NADP+ reductase final electron acceptor is NADP+ that is reduced to NADPH
  23. 23. NADP+ / NADPH NAD+ NADP+
  24. 24. Thylakoid Proteins: ATP Synthase protons pumped into the lumen pass through ATP synthase ATP produced in stroma photophosphorylation – light-dependent formation of ATP by chemiosmosis
  25. 25. Thylakoid Membrane Proteins
  26. 26. Non-cyclic Electron Flow: Z-Scheme
  27. 27. Non-cyclic Electron Transfer Summary 1. H2O is split to produce O2 (released from cell) and H+ ions (released into lumen) 2. enzyme complexes pump protons from stroma to lumen 3. NADP+ is final electron acceptor and produces NADPH 4. chemiosmosis to synthesize ATP
  28. 28. Light Reaction Animation Animation Link
  29. 29. Cyclic Electron Flow
  30. 30. Cyclic Electron Transfer Summary 1. only involves photosystem I (P700) 2. ferrodoxin returns electrons back to cytochrome complex (no need to split water to obtain electrons) 3. protons pumped into lumen to produce more ATP through chemiosmosis 4. no NADPH produced

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