Post on 18-Jan-2016
Need To Know• How photosystems convert light energy into
chemical energy. (There will be more on this in the next couple of days.)
• How photosystems convert solar energy to chemical energy.
• How linear electron flow in the light reactions results in the formation of ATP, NADPH, and O2
• How the formation of a proton gradient in the light reactions is used to for ATP from ADP and inorganic phosphate by ATP synthase.
Figure 8.11
Photon(fluorescence)
Groundstate
(b) Fluorescence
Excitedstate
Chlorophyllmolecule
Photon
Heat
e−
(a) Excitation of isolated chlorophyll molecule
En
erg
y o
f el
ectr
on
Figure 8.14
Photosystem II Photosystem I
NADPH
Millmakes
ATP
Ph
oto
n
Ph
oto
n
Figure 8.UN02
CalvinCycle
NADPH
NADP
ATP
ADP
Light
CO2
[CH2O] (sugar)
LightReactions
O2
H2O
Figure 8.12a
(a) How a photosystem harvests light
STROMA
THYLAKOID SPACE(INTERIOR OF THYLAKOID)
PhotonPrimaryelectronacceptor
Special pair ofchlorophyll amolecules
Transferof energy
Pigmentmolecules
Th
ylak
oid
mem
bra
ne
e−
Photosystem
Light-harvestingcomplexes
Reaction-centercomplex
There are two reaction centers
P680 P700
Linear electron flow
Figure 8.13-2
Photosystem II(PS II)
P680
Pigmentmolecules
Light
1
Primaryacceptor
22 H
O2
H2O
2
1 3
e−
e−
e−
ATP
Pq
Electrontransportchain
Cytochromecomplex
Pc
4
5Light
6
Pc
Primaryacceptor
Photosystem I(PS I)
P700
Light
6
NADPH
HNADP
reductase
NADP8e−
Fd
Electrontransportchain
7
Figure 8.16
Photosystem II Photosystem I
ToCalvinCycle
H
THYLAKOID SPACE(high H concentration)
Thylakoidmembrane
STROMA(low H concentration)
ATPsynthase
NADPH
e−
LightNADP
ATPADP
NADP
reductase
FdH
Pq
Pc
Cytochromecomplex
4 H
Light
2 HO2
H2O21
4 H
e−
1
2
3
Pi