0
PHOTOSYNTHESIS
Photosynthesis – synthesis using light
General Equation :
6CO2 + 6H2O C6H12O6 + 6O2
Mesophyll – most active photosynthetic...
Nature of Light
1. Light is both a particle and wave.
photon – particle
quantum – amount of energy of light
wavelength – d...
Absorption Spectrum
Absorption spectrum – a display of the amount
of light energy taken up by a molecule as a
function of the wavelength of li...
Absorption Spectrum of Chlorophyll
Change in Electronic State
Upon Absorption of Light Energy:
Chl + hv Chl*
Pathways for Excited Chlorophyll to dispose its
...
Action Spectrum
Photosynthetic Overview
Energy Transfer during Photosynthesis
Resonance transfer – excitation energy is conveyed from
the chlorophyll that absorbs...
Antenna Complexes
• Eukaryotes – within the chloroplast
• Prokaryotes – plasma membrane
Light Reactions : Concepts
Quantum Yield – number of photochemical
products per total number of
quanta absorbed
Hill react...
Z-scheme
Photosystems I and II : Differences
1. PS l produces a strong reductant, capable of
reducing NADP, and a weak oxidant.
2. ...
Chloroplast Structure
Electron Transfer in the Thylakoid
Membrane: 4 Protein complexes
Photochemical Event
1. Transfer of an electron from the chlorophyll
to an acceptor molecule:
chlorophyll is in oxidized st...
3. Pheophytin and 2 Quinones accept electrons
4. Electrons flow through Cytochromes b6f
complex
5. Plastoquinone and Plast...
Carbon Reactions
1. Calvin Cycle / Reductive Pentose Phosphate
Cycle / C3 Cycle
2. C4 Photosynthetic Carbon assimilation C...
Calvin Cycle : Stages
1. Carboxylation:
CO2 + RuBP 3- Phosphoglycerate
2. Reduction of 3- Phosphoglycerate to form
Glycera...
Carbon Reactions
Rubisco- Ribulose bisphosphate carboxylase/oxygenase
enzyme
Competition:O2and CO2 for the substrate Ribulose
bisphosphate
...
Regulation of the Calvin Cycle:
1. Light-dependent enzyme activation
Rubisco, NADP:glyceraldehyde-3-phosphate
dehydrogenas...
Photorespiration
Oxygenation – combination of Rubisco with
Oxygen instead of CO2.
- results to CO2 loss
Rise in temperatur...
C3 and C4 Leaf Anatomy
C4 Metabolism
1. CO2 fixation by PEP in mesophylly to form a
C4 acid ( malate or aspartate)
2. Transport of C4 acids to bu...
C4 Cycle
Advantage of C4 pathway
1. Concentrates CO2 in the bundle sheath cells
C4 Plants : Grasses, sugarcane, maize
2. Reduces ph...
Crassulacean Acid Metabolism
-enables plants to improve water use efficiently
1 g CO2: 400 to 500 g water loss forC3 and C...
Physiological and Ecological Considerations
of Photosynthesis
• Important Metabolic Steps for Optimum
Photosynthesis:
1. R...
Plant physio photosynthesis
Plant physio photosynthesis
Plant physio photosynthesis
Plant physio photosynthesis
Plant physio photosynthesis
Plant physio photosynthesis
Plant physio photosynthesis
Upcoming SlideShare
Loading in...5
×

Plant physio photosynthesis

752

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
752
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
36
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Transcript of "Plant physio photosynthesis"

  1. 1. PHOTOSYNTHESIS
  2. 2. Photosynthesis – synthesis using light General Equation : 6CO2 + 6H2O C6H12O6 + 6O2 Mesophyll – most active photosynthetic tissue Photosynthetic Reactions: 1. Thylakoid reactions 2. Carbon fixation reactions
  3. 3. Nature of Light 1. Light is both a particle and wave. photon – particle quantum – amount of energy of light wavelength – distance between crests frequency – no. of wave crests per unit time
  4. 4. Absorption Spectrum
  5. 5. Absorption spectrum – a display of the amount of light energy taken up by a molecule as a function of the wavelength of light Visible region –what our eyes are sensitive to Short wavelength – high frequency, high energy Long wavelength – low frequency , low energy
  6. 6. Absorption Spectrum of Chlorophyll
  7. 7. Change in Electronic State Upon Absorption of Light Energy: Chl + hv Chl* Pathways for Excited Chlorophyll to dispose its energy : 1. Fluorescence – re-emit a photon 2. Direct convertion to heat ; no emission of photon 3. Energy transfer 4. Photochemistry – energy causes occurence of chemical reactions
  8. 8. Action Spectrum
  9. 9. Photosynthetic Overview
  10. 10. Energy Transfer during Photosynthesis Resonance transfer – excitation energy is conveyed from the chlorophyll that absorbs the light to the reaction center
  11. 11. Antenna Complexes • Eukaryotes – within the chloroplast • Prokaryotes – plasma membrane
  12. 12. Light Reactions : Concepts Quantum Yield – number of photochemical products per total number of quanta absorbed Hill reactions : Robert Hill In the light, isolated chloroplast thylakoids reduce a variety of compounds, eg. Iron salts Enhancement effect : Robert Emerson The rate of photosynthesis was greater when red and far-red light were given together than the sum of their individual rates
  13. 13. Z-scheme
  14. 14. Photosystems I and II : Differences 1. PS l produces a strong reductant, capable of reducing NADP, and a weak oxidant. 2. PS ll produces a very strong oxidant, capable of oxidizing water, and a weaker reductant than he one produced by PS l 3. PS l : found in the stroma lamella and edges of grana lamella PS ll : predominantly located in the grana lamella Oxygenic organisms – Oxygen-evolving organisms
  15. 15. Chloroplast Structure
  16. 16. Electron Transfer in the Thylakoid Membrane: 4 Protein complexes
  17. 17. Photochemical Event 1. Transfer of an electron from the chlorophyll to an acceptor molecule: chlorophyll is in oxidized state – electron deficient Acceptor is in reduced state – electron rich 2. Water is oxidized to Oxygen by PS ll 2 H2O O2 + 4H+ + 4 e- protons – released into lumen of thylakoid, to stroma by ATP synthase
  18. 18. 3. Pheophytin and 2 Quinones accept electrons 4. Electrons flow through Cytochromes b6f complex 5. Plastoquinone and Plastocyanin carry electrons between PS ll and l 6. PS l Reaction Center Reduces NADP Interference in Photosynthetic Electron Flow: Herbicides : DCM (dichlorophenyl-dimethylurea) Paraquat
  19. 19. Carbon Reactions 1. Calvin Cycle / Reductive Pentose Phosphate Cycle / C3 Cycle 2. C4 Photosynthetic Carbon assimilation Cycle 3. Photorespiratory Carbon Oxidation Cycle
  20. 20. Calvin Cycle : Stages 1. Carboxylation: CO2 + RuBP 3- Phosphoglycerate 2. Reduction of 3- Phosphoglycerate to form Glyceraldehyde-3-phosphate 3. Regeneration of the CO2 acceptor , RuBP
  21. 21. Carbon Reactions
  22. 22. Rubisco- Ribulose bisphosphate carboxylase/oxygenase enzyme Competition:O2and CO2 for the substrate Ribulose bisphosphate Effect : Limits net CO2 fixation Autocatalytic- regeneration of biochemical intermediates Stoichiometry : 1/6 – for sucrose or starch production 5/6 – for regeneration of ribulose-1,5-bisphosphate
  23. 23. Regulation of the Calvin Cycle: 1. Light-dependent enzyme activation Rubisco, NADP:glyceraldehyde-3-phosphate dehydrogenase;fructose-1,6-bisphosphatase, Sedoheptulose-1,7—bisphosphatase, ribulose-5-phosphate kinase 2. Increases in Rubisco activity due to light 3. Light-dependent ion movements 4. Light-dependent membrane transport
  24. 24. Photorespiration Oxygenation – combination of Rubisco with Oxygen instead of CO2. - results to CO2 loss Rise in temperature effect: decrease in CO2 relative to O2 enhances the kinetic properties of Rubisco
  25. 25. C3 and C4 Leaf Anatomy
  26. 26. C4 Metabolism 1. CO2 fixation by PEP in mesophylly to form a C4 acid ( malate or aspartate) 2. Transport of C4 acids to bundle sheath cells 3. Decarboxylation of C4 acids within bundle sheath cells and generation of CO2 which is brought to Calvin cycle. 4. Transport of the C3 acid back to the mesophyll
  27. 27. C4 Cycle
  28. 28. Advantage of C4 pathway 1. Concentrates CO2 in the bundle sheath cells C4 Plants : Grasses, sugarcane, maize 2. Reduces photorespiration
  29. 29. Crassulacean Acid Metabolism -enables plants to improve water use efficiently 1 g CO2: 400 to 500 g water loss forC3 and C4 : 50 to 100 g water los for CAM plants Temporal and spatial separation : formation of C4 acids
  30. 30. Physiological and Ecological Considerations of Photosynthesis • Important Metabolic Steps for Optimum Photosynthesis: 1. Rubisco activity = low CO2; High light Intensity 2. Regeneration of RuBP = High CO2 ; Low Light 3. Metabolism of Triose Phosphates Light Parameters: 1. Spectral quality 3. Direction of Light 2. Amount of Light
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×