Download CH21 part2

CH21
PART2
生科3A
B983B0002 翁梨馨
B983B0044 楊濟鴻
reaction center (P870)
Single Reaction Center
electron transfer
Purple bacteria
Photosynthetic Units
ATP synthase
noncyclic
double Reaction Center
cytochrome bc1 electron transfer complex
PSII
ATP
reaction center (P680)
electron transfer
oxigen
cytochrome b6f complex
cyclic
PSI
reaction center (P700)
light-harvesting complex (LHC)
NADPH

Photosynthetic Units :
Many Chlorophyll Molecules
 Single Reaction Center


antenna chlorophylls :
Light is captured
 Routed


Chl•+ :

electron acceptor
CHLOROPHYLL FUNNELS THE
ABSORBED ENERGY TO REACTION
CENTERS BY EXCITON TRANSFER
a few chlorophyll molecules associated with the
photochemical reaction center
 other pigment :

light-harvesting
 antenna molecules

EXCITATION AND ELECTRON
TRANSFER
TRANSDUCTION OF LIGHT ENERGY INTO
CHEMICAL ENERGY INVOLVES OXIDATIONREDUCTION

Basis : light energy into chemical energy

Photon absorption


Chl → Chl*→molecule A→Chl•+ & AOxidation of A- →NADP+ to NADPH
PURPLE BACTERIA

Pigments:


Bacteriochlorophyll a or b, together with various
carotenoids
3 basic modules
reaction center (P870),
 cytochrome bc1 electron transfer complex,
 ATP synthase.


The light-driven
→ flow of electron
 → provides the energy for proton pumping by cyt bc1
complex
 → Powered by the proton gradient, ATP synthase
provides ATP.


QH2 is >30%

綠硫細菌


裂解H2S使電子變成不
循環的電子傳遞
不循環的電子傳遞 :
為了製造NADH
 還原能力保留

2H2O+2NADP++8 photons→O2+2NADPH+H+
Oxidation
PSⅡ （ photosystemⅡ）
>maximal red absorption at 680 nm
>quinones as terminal electron acceptors
>reaction center P680
proton
thylakoid membrane
P680
e-
Cytochrome
b6f
eoxidation
e-
PSⅠ
PSⅠ （ photosystemⅠ）
>maximal red absorption at 700 nm
> ferredoxins as terminal electron acceptors
>reaction center P700
Electrons carrier:
plastocyanin(soluble protein ), a one-electron carrier
Cyclic Photophosphorylation
Use PSI
Overcome the ATP deficit for CO2 fixation,
adjusts the ratio of ATP to NADPH produced
QUIZ 1

Characteristics of chlorophyll include all
EXCEPT:
1. iron-containing porphyrin.
2. planar conjugated porphyrin ring.
3. long-chain phytol tail.
4. delocalized 拍 electrons in the aromatic ring.
5. photoexcitable electrons.
QUIZ 2

All are properties of both the P700 and P680
reaction centers EXCEPT:
1. contain chlorophyll dimers.
2. are electron donors.
3. are activated by visible light.
4. are involved in light-driven O2 evolution.
5. all are properties.