Chapter 8 Light Reactions

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 O 2 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) Ground state (b) Fluorescence Excited state Chlorophyll molecule Photon Heat e−e− (a) Excitation of isolated chlorophyll molecule Energy of electron

Figure 8.14 Photosystem II Photosystem I NADPH Mill makes ATP Photon

Figure 8.UN02 Calvin Cycle NADPH NADP  ATP ADP Light CO 2 [CH 2 O] (sugar) Light Reactions O2O2 H2OH2O

Figure 8.12a (a) How a photosystem harvests light STROMA THYLAKOID SPACE (INTERIOR OF THYLAKOID) Photon Primary electron acceptor Special pair of chlorophyll a molecules Transfer of energy Pigment molecules Thylakoid membrane e−e− Photosystem Light- harvesting complexes Reaction- center complex

There are two reaction centers P680P700 Linear electron flow

Figure  Photosystem II (PS II ) P680 Pigment molecules Light 1 Primary acceptor 2 2 H  O2O2 H2OH2O  e−e− e−e− e−e− ATP Pq Electron transport chain Cytochrome complex Pc 4 5 Light 6 Pc Primary acceptor Photosystem I (PS I ) P700 Light 6 NADPH HH NADP  reductase  NADP  8 e−e− Fd Electron transport chain 7

Figure 8.16 Photosystem II Photosystem I To Calvin Cycle HH THYLAKOID SPACE (high H  concentration) Thylakoid membrane STROMA (low H  concentration) ATP synthase NADPH e−e− Light NADP  ATP ADP  NADP  reductase Fd HH  Pq Pc Cytochrome complex 4 H  Light  2 H  O2O2 H2OH2O  H  e−e− 1 23 P i