photosynthesis
TRANSCRIPT
![Page 1: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/1.jpg)
PHOTOSYNTHESIS
In 1780 Joseph Priestly discovered photosynthesis:
“…plants can “restore air which has been injured by the burning of candles.”
“…the air would neither extinguish a candle, nor was it all inconvenient to a mouse which I put into it.”
Stryer, Biochemistry, 4th ed.
![Page 2: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/2.jpg)
Biochem 3070 - Photosynthesis
• Photosynthesis provides essentially all free energy in biological systems by converting solar energy into chemical energy.
• Carbohydrates are formed from light-driven reactions that collectively appear deceptively simple:
CO2 + H2O + light CnH2nOn + O2
![Page 3: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/3.jpg)
Biochem 3070 - Photosynthesis
• Photosynthesis occurs in specialized organelles called chloroplasts:
Stryer, et.al., Biochemistry, 5th ed.
![Page 4: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/4.jpg)
Biochem 3070 - Photosynthesis
TEM of Chloroplast from Corn
Biochemistry, Voet & Voet,, 3rd Ed
![Page 5: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/5.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 6: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/6.jpg)
Biochem 3070 - Photosynthesis
• Photosynthesis consists of two sets of reactions:
the LIGHT and DARK reactions.
• The LIGHT-driven reactions are the primary events of photosynthesis; these occur in the thylakoid membrane.
• The DARK reactions occur in the stroma.
![Page 7: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/7.jpg)
Biochem 3070 - Photosynthesis
• The light-reactions of photosynthesis generate high-energy electrons that are used to form NADPH.
• On their way to NADPH, these high-energy electrons flow through a membrane-bound “electron transport” pathway, generating a proton motive potential (Δp) from which ATP is made.
![Page 8: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/8.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 9: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/9.jpg)
Biochem 3070 - Photosynthesis
![Page 10: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/10.jpg)
Biochem 3070 - Photosynthesis
Walker, et.al, Fundamentals of Chemistry, 1st ed.
![Page 11: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/11.jpg)
Biochem 3070 - Photosynthesis
Chlorophyll a:
Stryer, et.al., Biochemistry, 5th ed.
![Page 12: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/12.jpg)
Biochem 3070 - Photosynthesis
![Page 13: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/13.jpg)
Biochem 3070 - Photosynthesis
Sunlight spectrum, Chlorophyll a and Bacteriochlorophyll a
![Page 14: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/14.jpg)
Biochem 3070 - Photosynthesis
Voet & Voet, Biochemistry, 3rd ed., pg 875
![Page 15: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/15.jpg)
Biochem 3070 - Photosynthesis
• Light-harvesting Pigments help absorb wavelengths of light in the region of the spectrum where chlorophyll pigments do not absorb light.
• Photons absorbed by these pigments also transfer energy to chlorophyll.
β-carotene helps protect plants from photochemical reactions, expecially those involving oxygen; (it serves as an “antioxidant.”)
![Page 16: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/16.jpg)
Biochem 3070 - Photosynthesis
![Page 17: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/17.jpg)
Biochem 3070 - Photosynthesis
The majority of chlorophyll molecules in a photosynthetic unit do not get involved in photosynthesis directly. Rather, they transfer their absorbed energy to a reaction center complex.
C C C C C
C C C C C C C C C C
C C C C C C C C C C C
C C C C C C C C C C C C C
C C C C C C C C C C C C
C C C C C C C C C C C C C C
C C C C C C C C C C C
C C C C C C C C C C
C C C C C C C C C
C C C C C
![Page 18: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/18.jpg)
Biochem 3070 - Photosynthesis
Light energy absorbed by antenna chlorophyll molecules and auxillary pigments is transferred to specialized reaction centers.
This energy transfer (often called “resonance energy transfer” or “exciton hopping”) is very efficient, approaching 100%!
![Page 19: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/19.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 20: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/20.jpg)
Biochem 3070 - Photosynthesis
Voet & Voet, Biochemistry, 3rd ed., pg 877
![Page 21: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/21.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 22: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/22.jpg)
Biochem 3070 - Photosynthesis
Voet & Voet, Biochemistry, 3rd ed., pg 877
![Page 23: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/23.jpg)
Biochem 3070 - Photosynthesis
Voet & Voet, Biochemistry, 3rd ed., pg 877
![Page 24: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/24.jpg)
Biochem 3070 - Photosynthesis
Garrett & Grisham, Biochemistry, 3rd ed.
![Page 25: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/25.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 26: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/26.jpg)
Biochem 3070 - Photosynthesis
X-ray Structure of Photosystem II (S. elongatus)
Stryer, et.al., Biochemistry, 5th ed.
![Page 27: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/27.jpg)
Biochem 3070 - Photosynthesis
Voet & Voet, Biochemistry, 3rd ed., pg 888
X-ray Structure of Photosystem II (S. elongatus)
![Page 28: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/28.jpg)
Biochem 3070 - Photosynthesis
Mn cluster in the OEC
Schematic mechanism of oxygen generation in PSII:
Voet & Voet, Biochemistry, 3rd ed., pg 889
![Page 29: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/29.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 30: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/30.jpg)
Biochem 3070 - Photosynthesis
Voet & Voet, Biochemistry, 3rd ed., pg 877
![Page 31: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/31.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 32: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/32.jpg)
Biochem 3070 - Photosynthesis
Herbicides that inhibit Photosystem II by blocking the transfer of electrons to QH2:
Stryer, et.al., Biochemistry, 5th ed.
![Page 33: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/33.jpg)
Biochem 3070 - Photosynthesis
Voet & Voet, Biochemistry, 3rd ed., pg 877
![Page 34: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/34.jpg)
Biochem 3070 - Photosynthesis
Electron Flow through PSII: Electron Flow through Cytochrome bf:
Plastocyanin:
Stryer, et.al., Biochemistry, 5th ed.
![Page 35: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/35.jpg)
Biochem 3070 - Photosynthesis
• Photosystem I:
Stryer, et.al., Biochemistry, 5th ed.
![Page 36: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/36.jpg)
Biochem 3070 - Photosynthesis
Photosystem I:
700nm photon
Stryer, et.al., Biochemistry, 5th ed.
![Page 37: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/37.jpg)
Biochem 3070 - PhotosynthesisFerredoxin Structure
Stryer, et.al., Biochemistry, 5th ed.
![Page 38: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/38.jpg)
Biochem 3070 - Photosynthesis
“Z-Scheme” of Photosynthesis:
Stryer, et.al., Biochemistry, 5th ed.
![Page 39: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/39.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 40: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/40.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 41: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/41.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
![Page 42: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/42.jpg)
Biochem 3070 - Photosynthesis
Stryer, et.al., Biochemistry, 5th ed.
Andre Jagendorf and Ernest Uribe’s classic experiment, showing the production of ATP from an artificially induced proton gradient across isolated chloroplasts in the absence of any light!
(First Reported in 1965)
![Page 43: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/43.jpg)
Biochem 3070 - Photosynthesis
![Page 44: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/44.jpg)
Biochem 3070 - Photosynthesis
Stroma
Lumen
(Thylakoid Space)
![Page 45: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/45.jpg)
Biochem 3070 - Photosynthesis
Stroma
Lumen
Inner-membrane Space
Matrix
Stryer, et.al., Biochemistry, 5th ed.
![Page 46: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/46.jpg)
Biochem 3070 - Photosynthesis
What about CO2?
CO2 + H2O + light CnH2nOn + O2
![Page 47: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/47.jpg)
Biochem 3070 - Photosynthesis
Melvin Calvin discovered the CO2 acceptor by using C-14 radioactive labeled carbon dioxide:
He discovered that the reactions of CO2 fixation are almost identical to reactions of the phosphate shunt:
Stryer, et.al., Biochemistry, 5th ed.
![Page 48: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/48.jpg)
Biochem 3070 - Photosynthesis
The Calvin Cycle:
From light-driven reactions
Stryer, et.al., Biochemistry, 5th ed.
![Page 49: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/49.jpg)
Biochem 3070 - Photosynthesis
Ribulose 1,5-bisphosphate carboxylase/oxygenase [“rubisco”]:
Rubisco consitutes more than 16% of all protein in chloroplasts.
It is the most abundant protein in the entire biosphere!
Stryer, et.al., Biochemistry, 5th ed.
![Page 50: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/50.jpg)
Biochem 3070 - Photosynthesis
Proposed mechanism for Rubisco:
Stryer, et.al., Biochemistry, 5th ed.
![Page 51: Photosynthesis](https://reader036.vdocuments.mx/reader036/viewer/2022070301/544e2efcb1af9f130a8b45cc/html5/thumbnails/51.jpg)
End of Slides
For
Photosynthesis
Credits: Many of the diagrams used in these slides were taken from Stryer, et.al, Biochemistry, 5th Ed., Freeman Press (in our course textbook) and from prior editions of this text.