PHOTOSYNTHESIS.pdf

PHOTOSYNTHESIS
Harvesting the Solar Energy
1
PHOTOSYNTHESIS
2
PHOTOSYNTHESIS
3
PHOTOSYNTHESIS
CONTENT
✓Definition
✓Photosynthetic pigments
✓Process-
4
PHOTOSYNTHESIS
•HILL REACTION
•RED-DROP &
EMERSON EFFECT
•PHOTOSYSTEMS
•Z-SCHEME
LIGHT
REACTION
•CALVIN CYCLE
•HATCH & SLACK
PATHWAY
•CAM PATHWAY
DARK
REACTION
PHOTOSYNTHESIS
6
PIGMENTS
➢ Requires absorption of light
➢ PIGMENTS-
➢ CHLOROPHYLL – Primary pigment
➢ CAROTENOIDS – accessory pigment
➢ PHYCOBILINS – accessory pigment
7
PHOTOSYNTHESIS
CHLOROPHYLL
➢ Chl. a, Chl. b, Chl. c, Chl. d, Chl. e, Bacteriochl.
etc.
➢ Porphyrin derivative
➢ Cyclic tetrapyrrolic str.
➢ Porphyrin ring & Phytol tail
➢ Empirical formula-
Chl.a – C55 H72 O5 N4 Mg
Chl.b – C55 H70 O6 N4 Mg
➢ Peaks of absorption – Chl. a - 662 & 430 nm
Chl. b - 642 & 454 nm 8
PHOTOSYNTHESIS
PHOTOSYNTHESIS
9
Phytol tail
PHOTOSYNTHESIS
10
11
PHOTOSYNTHESIS
ABSORPTION SPECTRUM
CAROTENOIDS
➢ Orange-Yellow pigments
➢ 2 types-
Carotenes Xanthophylls
-Orange - Red -Yellow
-Most common-β Carotene - Oxygenated carotenes
➢ Absorb λ not absorbed by Chl.
➢ Prevents photo-oxidation of Chl. by absorbing excess light
energy
12
PHOTOSYNTHESIS
PHYCOBILINS
➢ Open chain tetrapyrroles
➢ Water sol. complexes of proteins & bile
pigments
➢ Red algae & Cyanobacteria
➢ 3 Photosynthetic Phycobilins-
*Phycocyanin
*Phycoerythrin
*Allophycocyanin 13
PHOTOSYNTHESIS
PROCESS
➢ Oxi.-Red. Reaction - H2O oxi O2
CO2 red. Carbohydrates
➢ 6CO2+12H2O C6H12O6+6O2+6H2O
14
PHOTOSYNTHESIS
LIGHT REACTION
➢ Site – Grana (Thyllakoid membrane)
➢ Dependent on light
➢ Water – oxidised
➢ Oxygen – evolved
➢ Energy produced as ATP & NADPH
15
PHOTOSYNTHESIS
HILL REACTION:
✓ The source of oxygen which is evolved during the
photosynthesis is water. In 1937, an English bio-chemist
named, Robin Hill proved this idea by a reaction. This
reaction is named as Hill reaction.
✓ Isolated chloroplast release O2 in presence of suitable
electron acceptor (Hill reagent DCPIP)
✓ Light driven split of water in absence of CO2 fixation-Hill
reaction
✓ Ruben & Kamen (1940s)-
6CO2+12H2O18 C6H12O6+6O2
18+6H2O 16
PHOTOSYNTHESIS
RED DROP & EMERSON ENHANCEMENT EFFECT:
✓ 2 quanta light energy – required – drive 1 electron
from water to NADP+
✓ for red. of 1 CO2 – 4 electrons
✓ Therefore 8 quanta -1 CO2 red./1O2production
✓ No. of oxygen mol. released = Quantum Yield
Quanta
= 1/8
18
PHOTOSYNTHESIS
✓ Emerson & Lewis –
*Q.Y. decreases sharply – λ ˃ 680nm (red zone)
- Red Drop
*If λ ˂ & ˃ 680nm provided simultaneously – Q.Y.
much greater than could be from adding rates when
either λ was provided alone – Emerson enhancement
effect
19
PHOTOSYNTHESIS
PHOTOSYNTHESIS
20
A
A
A
A
A
A
A
A
RED DROP
PHOTOSYNTHESIS
21
COMPONENTS OF LIGHT
REACTION
PHOTOSYSTEMS
LIGHT HARVESTING
COMPLEXES
*Chl.a,chl.b,xanthophyll
*little βcarotene
*assists in light absorption
ATPase
COMPLEX/COUPLING
FACTOR
*catalyses ATP
synthesis
22
PHOTOSYNTHESIS
PS I
•Stroma thylakoids
•Chl.a,chl.b,βcarotene
•Reaction centre P700
•Plastocyanin,FRS
PS II
•Grana thylakoids
•Chl.a,chl.b,βcarotene
•P680,phaeophytin
•Plastoquinone,Mn
proteins
•Cyt.b6f ccomplex
PHOTOSYNTHETIC ELECTRON TRANSPORT
CHAIN
23
PHOTOSYNTHESIS
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
PS
II
P680
Phaeo
PSI P700
P430
H2O
1/2O2+2H
+
e-
PQ
Cytb6f
PC
FR
S Fd
NADP NADPH
NON-CYCLIC ELECTRON
TRANSPORT CHAIN
PHOTOSYNTHESIS
24
PHOTOSYNTHESIS
26
PHOTOPHOSPHORYLATION
➢ Formation of ATP in presence of light
➢ Mechanism –
*Chemical coupling hypothesis - Slater
*Conformational coupling hypo. - P. D. Boyer
*Chemi-osmotic coupling hypo. - P. Mitchell
27
PHOTOSYNTHESIS
CHEMI-OSMOTIC COUPLING HYPOTHESIS
28
PHOTOSYNTHESIS
DARK REACTION
➢ Reductive Pentose Phosphate pathway /
Calvin Cycle / Bassham & Calvin Cycle /
Blackman Reaction / Photosyn. Carbon
Reduction Cycle / C3 Cycle
➢ Steps-
29
PHOTOSYNTHESIS
Synthesis of
Carbohydrates
Regeneration
of RuBP
6 RuBP
12 3PGA
12 G3P
3 G3P +
3 DHAP
3 FDP
3 F6P
2 F6P +
2 G3P
2 X5P +
2 E4P
2 E4P +
2 DHAP
2 SDP
2 S7P +
2 G3P
2 R5P +
2 X5P
4 X5P +
2 Ru5P
6 Ru5P
6CO2
RuBP
Carboxylase
12NADPH
12ATP
12NADP
12ADP
G3P
Dehydrogenase
PGA Kinase
Isomerase
FDP
Aldolase
Hexose
Diphosphatse
3 iP
G6P
Glucose P
Isomerase
GLUCOSE
Phosphatase
iP
Aldolase
Diphosphatase
2 iP
Transketolase
Ribose P
Isomerase
Ribose P
Epimerase
6ATP
6ADP
30
PHOTOSYNTHESIS
HATCH & SLACK PATHWAY / COOPERATIVE
PHOTOSYNTHESIS / C4 PATHWAY
➢ Eg. Saccharum, Zea mays, Amaranthus,
Atriplex, Cyperus etc.
➢ C4 plants – Specific anatomical, Physio. &
Biochem. Characteristics that constitute
C4 syndrome –
✓ 2 types of photosynthetic cells
✓ Each vas. bundle is surrounded by a layer of cells –
BUNDLE SHEATH CELLS
31
PHOTOSYNTHESIS
✓Bundle sheath cells-surrounded by one or more
layers of mesophyll cells – this structural
specialization – KRANZ ANATOMY
✓Tropical or sub-tropical in origin
✓Better equipped to withstand drought
✓Maintain active photosynthesis under water stress
32
PHOTOSYNTHESIS
SUB-TYPES
NADP-ME
TYPE
Eg. Zea,
Saccharum
NAD-ME
TYPE
Eg. Chloris,
Elusine
PEP-CK TYPE
Eg.
Muhlenbergia,
Sporobolus
34
PHOTOSYNTHESIS
C4 CYCLE
35
PHOTOSYNTHESIS
MESOPHYLL CELL BUNDLE SHEATH CELL
NADP-ME TYPE
OAA MALIC ACID
PEP PYRUVATE
MALATE
PYRUVATE
36
PHOTOSYNTHESIS
CO2
NADPH NAD
P
Malate
Dehydrogenase
CO2
NADPH
NADP
C3
cycle
2ATP
2ADP
Pyruvate P
Dikinase
NADP
-ME
PEP-Carboxylase
MESOPHYLL CELL BUNDLE SHEATH CELL
NAD-ME TYPE
OAA ASPARTATE
PEP PYRUVATE ALANINE
ASPARTATE OAA
MALATE
ALANINE PYRUVATE
NADH
NAD
Malate
Dehydrogenase
2ATP
2ADP
NAD
NADH
NAD-ME
CO2
CO2
C3
cycle
PEP-Carboxylase
Transaminase Transaminase
Transaminase
Transaminase
Pyruvate P
Dikinase
37
PHOTOSYNTHESIS
MESOPHYLL CELL BUNDLE SHEATH CELL
PEP-CK TYPE
OAA ASPARTATE
PEP PYRUVATE ALANINE
ASPARTATE OAA
ALANINE PEP
CO2
CO2
Transaminase Transaminase
Transaminase
ATP
ADP
2ATP
2ADP
PEP-CK
Pyruvate P
Dikinase
PEP-Carboxylase
C3
cycle
38
PHOTOSYNTHESIS
CAM PATHWAY
➢ Crassulaceae, cactaceae, orchidaceae,
bromeliaceae, liliaceae, euphorbiaceae
➢ CAM plants-
➢ Nocturnal stomatal opening
➢ Large vacuoles in chlorophyllous cells
➢ Formation of malic at night, disappears during day
time
39
PHOTOSYNTHESIS
PHOTOSYNTHESIS
40
PHOTOSYNTHESIS
42
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PHOTOSYNTHESIS.pdf

  • 1. PHOTOSYNTHESIS Harvesting the Solar Energy 1 PHOTOSYNTHESIS
  • 4. CONTENT ✓Definition ✓Photosynthetic pigments ✓Process- 4 PHOTOSYNTHESIS •HILL REACTION •RED-DROP & EMERSON EFFECT •PHOTOSYSTEMS •Z-SCHEME LIGHT REACTION •CALVIN CYCLE •HATCH & SLACK PATHWAY •CAM PATHWAY DARK REACTION
  • 6. PIGMENTS ➢ Requires absorption of light ➢ PIGMENTS- ➢ CHLOROPHYLL – Primary pigment ➢ CAROTENOIDS – accessory pigment ➢ PHYCOBILINS – accessory pigment 7 PHOTOSYNTHESIS
  • 7. CHLOROPHYLL ➢ Chl. a, Chl. b, Chl. c, Chl. d, Chl. e, Bacteriochl. etc. ➢ Porphyrin derivative ➢ Cyclic tetrapyrrolic str. ➢ Porphyrin ring & Phytol tail ➢ Empirical formula- Chl.a – C55 H72 O5 N4 Mg Chl.b – C55 H70 O6 N4 Mg ➢ Peaks of absorption – Chl. a - 662 & 430 nm Chl. b - 642 & 454 nm 8 PHOTOSYNTHESIS
  • 11. CAROTENOIDS ➢ Orange-Yellow pigments ➢ 2 types- Carotenes Xanthophylls -Orange - Red -Yellow -Most common-β Carotene - Oxygenated carotenes ➢ Absorb λ not absorbed by Chl. ➢ Prevents photo-oxidation of Chl. by absorbing excess light energy 12 PHOTOSYNTHESIS
  • 12. PHYCOBILINS ➢ Open chain tetrapyrroles ➢ Water sol. complexes of proteins & bile pigments ➢ Red algae & Cyanobacteria ➢ 3 Photosynthetic Phycobilins- *Phycocyanin *Phycoerythrin *Allophycocyanin 13 PHOTOSYNTHESIS
  • 13. PROCESS ➢ Oxi.-Red. Reaction - H2O oxi O2 CO2 red. Carbohydrates ➢ 6CO2+12H2O C6H12O6+6O2+6H2O 14 PHOTOSYNTHESIS
  • 14. LIGHT REACTION ➢ Site – Grana (Thyllakoid membrane) ➢ Dependent on light ➢ Water – oxidised ➢ Oxygen – evolved ➢ Energy produced as ATP & NADPH 15 PHOTOSYNTHESIS
  • 15. HILL REACTION: ✓ The source of oxygen which is evolved during the photosynthesis is water. In 1937, an English bio-chemist named, Robin Hill proved this idea by a reaction. This reaction is named as Hill reaction. ✓ Isolated chloroplast release O2 in presence of suitable electron acceptor (Hill reagent DCPIP) ✓ Light driven split of water in absence of CO2 fixation-Hill reaction ✓ Ruben & Kamen (1940s)- 6CO2+12H2O18 C6H12O6+6O2 18+6H2O 16 PHOTOSYNTHESIS
  • 16. RED DROP & EMERSON ENHANCEMENT EFFECT: ✓ 2 quanta light energy – required – drive 1 electron from water to NADP+ ✓ for red. of 1 CO2 – 4 electrons ✓ Therefore 8 quanta -1 CO2 red./1O2production ✓ No. of oxygen mol. released = Quantum Yield Quanta = 1/8 18 PHOTOSYNTHESIS
  • 17. ✓ Emerson & Lewis – *Q.Y. decreases sharply – λ ˃ 680nm (red zone) - Red Drop *If λ ˂ & ˃ 680nm provided simultaneously – Q.Y. much greater than could be from adding rates when either λ was provided alone – Emerson enhancement effect 19 PHOTOSYNTHESIS
  • 20. COMPONENTS OF LIGHT REACTION PHOTOSYSTEMS LIGHT HARVESTING COMPLEXES *Chl.a,chl.b,xanthophyll *little βcarotene *assists in light absorption ATPase COMPLEX/COUPLING FACTOR *catalyses ATP synthesis 22 PHOTOSYNTHESIS PS I •Stroma thylakoids •Chl.a,chl.b,βcarotene •Reaction centre P700 •Plastocyanin,FRS PS II •Grana thylakoids •Chl.a,chl.b,βcarotene •P680,phaeophytin •Plastoquinone,Mn proteins •Cyt.b6f ccomplex
  • 24. PHOTOPHOSPHORYLATION ➢ Formation of ATP in presence of light ➢ Mechanism – *Chemical coupling hypothesis - Slater *Conformational coupling hypo. - P. D. Boyer *Chemi-osmotic coupling hypo. - P. Mitchell 27 PHOTOSYNTHESIS
  • 26. DARK REACTION ➢ Reductive Pentose Phosphate pathway / Calvin Cycle / Bassham & Calvin Cycle / Blackman Reaction / Photosyn. Carbon Reduction Cycle / C3 Cycle ➢ Steps- 29 PHOTOSYNTHESIS Synthesis of Carbohydrates Regeneration of RuBP
  • 27. 6 RuBP 12 3PGA 12 G3P 3 G3P + 3 DHAP 3 FDP 3 F6P 2 F6P + 2 G3P 2 X5P + 2 E4P 2 E4P + 2 DHAP 2 SDP 2 S7P + 2 G3P 2 R5P + 2 X5P 4 X5P + 2 Ru5P 6 Ru5P 6CO2 RuBP Carboxylase 12NADPH 12ATP 12NADP 12ADP G3P Dehydrogenase PGA Kinase Isomerase FDP Aldolase Hexose Diphosphatse 3 iP G6P Glucose P Isomerase GLUCOSE Phosphatase iP Aldolase Diphosphatase 2 iP Transketolase Ribose P Isomerase Ribose P Epimerase 6ATP 6ADP 30 PHOTOSYNTHESIS
  • 28. HATCH & SLACK PATHWAY / COOPERATIVE PHOTOSYNTHESIS / C4 PATHWAY ➢ Eg. Saccharum, Zea mays, Amaranthus, Atriplex, Cyperus etc. ➢ C4 plants – Specific anatomical, Physio. & Biochem. Characteristics that constitute C4 syndrome – ✓ 2 types of photosynthetic cells ✓ Each vas. bundle is surrounded by a layer of cells – BUNDLE SHEATH CELLS 31 PHOTOSYNTHESIS
  • 29. ✓Bundle sheath cells-surrounded by one or more layers of mesophyll cells – this structural specialization – KRANZ ANATOMY ✓Tropical or sub-tropical in origin ✓Better equipped to withstand drought ✓Maintain active photosynthesis under water stress 32 PHOTOSYNTHESIS
  • 30. SUB-TYPES NADP-ME TYPE Eg. Zea, Saccharum NAD-ME TYPE Eg. Chloris, Elusine PEP-CK TYPE Eg. Muhlenbergia, Sporobolus 34 PHOTOSYNTHESIS
  • 32. MESOPHYLL CELL BUNDLE SHEATH CELL NADP-ME TYPE OAA MALIC ACID PEP PYRUVATE MALATE PYRUVATE 36 PHOTOSYNTHESIS CO2 NADPH NAD P Malate Dehydrogenase CO2 NADPH NADP C3 cycle 2ATP 2ADP Pyruvate P Dikinase NADP -ME PEP-Carboxylase
  • 33. MESOPHYLL CELL BUNDLE SHEATH CELL NAD-ME TYPE OAA ASPARTATE PEP PYRUVATE ALANINE ASPARTATE OAA MALATE ALANINE PYRUVATE NADH NAD Malate Dehydrogenase 2ATP 2ADP NAD NADH NAD-ME CO2 CO2 C3 cycle PEP-Carboxylase Transaminase Transaminase Transaminase Transaminase Pyruvate P Dikinase 37 PHOTOSYNTHESIS
  • 34. MESOPHYLL CELL BUNDLE SHEATH CELL PEP-CK TYPE OAA ASPARTATE PEP PYRUVATE ALANINE ASPARTATE OAA ALANINE PEP CO2 CO2 Transaminase Transaminase Transaminase ATP ADP 2ATP 2ADP PEP-CK Pyruvate P Dikinase PEP-Carboxylase C3 cycle 38 PHOTOSYNTHESIS
  • 35. CAM PATHWAY ➢ Crassulaceae, cactaceae, orchidaceae, bromeliaceae, liliaceae, euphorbiaceae ➢ CAM plants- ➢ Nocturnal stomatal opening ➢ Large vacuoles in chlorophyllous cells ➢ Formation of malic at night, disappears during day time 39 PHOTOSYNTHESIS