Photosynthesis 1

1,576 views

Published on

Photosynthesis overview
A. Purpose
B. Location
The light vs. the “dark” reaction
Chloroplasts pigments
A. Light absorption
B. Types
Light reactions
A. Photosystems
B. Photophosphorylation
V. The light independent reaction (“dark” reaction)
A. Carbon “fixation”
B. Reduction
C. Regeneration
VI. Alternative plants

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

No Downloads
Views
Total views
1,576
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
67
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide

Photosynthesis 1

  1. 1. Photosynthesis By: Muhammad Iqbal Khan SS Biology Email ID mikhan1313@yahoo.com Contact: 0923135448175
  2. 2. Lecture 3 Outline (Ch. 8) I. Photosynthesis overview A. Purpose B. Location I. The light vs. the “dark” reaction II. Chloroplasts pigments A. Light absorption B. Types IV. Light reactions A. Photosystems B. Photophosphorylation V. The light independent reaction (“dark” reaction) A. Carbon “fixation” B. Reduction C. Regeneration VI. Alternative plants
  3. 3. Photosynthesis - overview
  4. 4. Overall purpose: Photosynthesis - overview • photosynthesis – light chemical energy • complements respiration Energy for all life on earth ultimately comes from photosynthesis
  5. 5. Cellular Respiration: (Exergonic) Photosynthesis: (Endergonic) Cellular Respiration vs. Photosynthesis
  6. 6. Photosynthesis – chloroplast recap Outer membrane Inner membrane Thylakoid membrane Stroma Thylakoid space Intermembrane space
  7. 7. Photosynthesis - overview • Photosynthesis - 1. light rxn: store energy & split water – “photo” 2. dark rxn: “fix” CO2 & make sugars – “synthesis” Calvin cycle NADPH & ATP
  8. 8. Redox Reactions Equation for photosynthesis 6CO2 + 12H2O + light energy C6H12O6 + 6O2 + 6H2O
  9. 9. Photosynthesis - overview – thylakoid membrane – thylakoid space – stroma • light reactions: • dark reactions: Light H2O Chloroplast Light Reactions NADP+ P ADP + ATP NADPH O2 Calvin Cycle CO2 [CH2O] (sugar)
  10. 10. Photosynthesis – light absorption • visible light ~380 to 750 nm • chloroplast pigments – abs blue-violet & red - transmit and reflect green
  11. 11. • pigments: • chlorophyll a • accessory pigments -energy-absorbing ring -hydrocarbon tail - carotenoids - photoprotective Photosynthesis – light absorption - chlorophyll b
  12. 12. • chlorophyll a – abs blue-violet, red 400-450, 650-700 nm • chlorophyll b & carotenoids – abs broadly blue-violet mid-400s • more wavelengths used for photosynthesis = more light energy absorbed Photosynthesis – light absorption
  13. 13. • chlorophyll abs light Photosynthesis – light absorption • e- excited • more energy • energy transferred Pigments have two states: ground & excited
  14. 14. Photosynthesis – light absorption light harvesting complex • energy absorbed from light - to pigments • to reaction center - two special chlorophyll a - 1° electron acceptor • light harvesting complex & reaction center = photosystem (PS) - proteins Pigments are held by proteins in the thylakoid membranes
  15. 15. Photosynthesis – energy transfer • Photosystem I (PS I) & PS II • Difference – light wavelength, proteins,  where e- from Light Thylakoid membrane THYLAKOID SPACE STROMA Photosystem II Photosystem I Light
  16. 16. Photosynthesis – energy transfer • PSII: absorbs 680 nm, • PS I: absorbs 700 nm, (less energy) splits water, powerful ETC, ATP made e- from PSII, short ETC, NADPH made
  17. 17. Photosynthesis – energy transfer • e- from PS II electron transport chain (ETC) PS I  NADPH• e- from PS I 2nd ETC e- carrier: NADP+ • e- in PS II, from split H20
  18. 18. Photosynthesis – chemiosmosis • How is ATP produced? Chemiosmosis photophosphorylation • e- down ETC, H+ to thylakoid space • H+ conc. gradient • H+ down gradient, ATP synthase
  19. 19. Light reaction - summary • inputs: light energy, H2O • PS II, ETC, PS I, ETC • outputs: ATP NADPH O2 (waste)
  20. 20. Self-Check Step of Photosynthesis Location IN chloroplast Inputs Outputs ATP produced? (don’t need #) e- carriers loaded? Light reaction overall PSII PSI “Dark” reaction overall Know figures of chloroplast reactions/locations! 
  21. 21. Photosynthesis – energy transfer
  22. 22. “Dark” reaction (Light-independent Reaction) 6CO2 + 12H2O + light energy C6H12O6 + 6O2 + 6H2O • “Dark” reaction: Calvin cycle • regenerative • anabolic • CO2 in, sugar out • during daylight CO2 NADP+ ADP Pi+ RuBP 3-Phosphoglycerate Calvin Cycle G3PATP NADPH Starch (storage) Sucrose (export) Chloroplast Light H2O O2
  23. 23. Carbon fixation • 3 stages of Calvin-cycle: • #1 – carbon fixation • CO2 link to 5-C • 5-C: ribulose bisphosphate (RuBP) - enzyme: Rubisco abundant • 6-C unstable – split  2(3-C)
  24. 24. Reduction • #2 – reduction • reduced 3-C: G3P • 3-C reduced • e- from NADPH • 3 stages of Calvin-cycle:
  25. 25. Regeneration of C-acceptor • multiple steps • uses ATP • every 3 cycles: 1 G3P made 3 RuBP regenerated • #3 – regenerate C-acceptor • still 5 G3P  3 RuBP • C3 plants – CO2 fixed into 3-C • 3 stages of Calvin-cycle:
  26. 26. Self-Check Step of Photosynthesis Location IN chloroplast Inputs Outputs ATP produced (don’t need #) e- carriers loaded Light reaction overall PSII PSI “Dark” reaction overall
  27. 27. Alternate methods of C fixation
  28. 28. Alternate methods of C fixation CO2 NADP+ ADP Pi+ RuBP 3-Phosphoglycerate Calvin Cycle G3PATP NADPH Starch (storage) Sucrose (export) Chloroplast Light H2O O2 • CO2 in  stomata • open, lose water • O2 fixed – photorespiration – inefficient • hot, dry – open stomata less; lowers water loss, lowers CO2 • fix CO2 into 4-C molecules
  29. 29. Photosynthesis – summary • light reaction: Light energy + H2O • light-independent: CO2, NADPH, ATP O2, NADPH, ATP Thylakoids G3P (sugar), RuBP Stroma
  30. 30. Photosynthesis – summary Where do photosynthetic products go?
  31. 31. Photosynthesis – in context of big picture
  32. 32. Lecture 3 Summary 1. Photosynthesis Overview (Ch. 8) - Purpose - Redox reactions - Electron carriers & sugars 2. Light (Ch. 8) - Absorption pigments - Light spectra/wavelengths 3. Locations of steps, inputs/outputs, purpose, description (Ch. 8) - PSI vs. PS II - Whole light reaction [includes chemiosmosis] - “dark” reaction/Calvin cycle [3 steps] 4. Alternate modes of photosynthesis (Ch. 8) 5. Photosynthesis context (Ch. 8) - Uses for products - Relationship of cell respiration and photosynthesis

×