Central metabolism glucose oxidative phosphorylation TCA cycle glycolysis fermentation organic wastes CO 2 ATP acetyl CoA polysaccharides lipids amino acids proteins  Where do the molecules we eat come from?

Photosynthesis  Ultimate source of carbon and energy for all living things

Halobacterium: Simplest photosynthesis  Bacteriorhodopsin uses light energy to pump protons H+H+ outside cytoplasm H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ ATP synthase H+H+ H+H+ H+H+ ADP ATP bacteriorhodopsin light

Plants have been doing this for a while…

Plant photosynthesis overview  Light powers ATP synthesis  CO 2 + ATP used to synthesize glucose light energy ATP CO 2 glucose

Reactions of photosynthesis  Light-dependent: capture energy as ATP and NADPH  Light-independent: CO 2 → glucose (“fix” carbon) light energy ATP CO 2 glucose 6 CO H 2 O + Light Energy  C 6 H 12 O O 2

The chloroplast  Light-dependent reactions in thylakoid membrane  Light-independent reactions in stroma thylakoid space t.m. i.m. o.m. granum stroma

Light-dependent reactions  Capture light energy as ATP and NADPH  Occur in thylakoid membrane free energy (G) e- photosystem II photosystem I light ATP ADP NADPH NADP

Chlorophyll  Light-harvesting pigment in thylakoid membrane  Lipid-like structure with large carbon ring  Absorbs blue and red wavelengths of light (reflects back green)

Photosystem II  “Satellite dish” of chlorophyll in membrane  Light-gathering “antenna” molecules  Pass energy to “reaction center” or (“special pair”) chlorophyll light

Photosystem II  Reaction center chlorophyll oxidizes H 2 O → O 2  Using light energy, energizes e –  Transfers e – to electron transport chain light H2OH2O O2O2 e–e– electron carrier e- photosystem II light

 Electron transport  Cytochrome oxidase complex pumps H + into thylakoid space  Electrons transferred to Photosystem I Photosystem II stroma thylakoid space H2OH2O O2O2 H+H+ H+H+ e–e– H+H+ H+H+ H+H+ H+H+ H+H+ cytochrome oxidase complex photosystem II photosystem I

 H + gradient used to synthesize ATP Photosystem II stroma thylakoid space H2OH2O O2O2 H+H+ H+H+ e–e– H+H+ H+H+ H+H+ H+H+ H+H+ cytochrome oxidase complex photosystem II H+H+ H+H+ H+H+ H+H+ H+H+ ATP synthase H+H+ H+H+ ADP ATP

Photosystem I  Second chlorophyll complex  Re-energizes “used” electron free energy (G) e- NADPH photosystem II photosystem I light ATP ADP NADP

 Electron transport  Electron transferred to NADP + → NADPH  Electrons transferred to Photosystem I Photosystem I stroma thylakoid space H2OH2O O2O2 H+H+ H+H+ e–e– H+H+ H+H+ H+H+ H+H+ H+H+ cytochrome oxidase complex photosystem II photosystem I NADP + NADPH

Light-dependent reactions  Capture light energy as ATP and NADPH  Why does the plant want NADPH? free energy (G) e- photosystem II photosystem I light ATP ADP NADPH NADP

Light-independent (“dark”) reactions  Why does the plant want to make glucose? CO 2 glucose ATPNADPH

Light-independent (“dark”) reactions  CO 2 reduced to make glucose  Occurs in stroma  Calvin cycle CO 2 glucose ATP NADPH 3C carbohydrate

Light-independent (“dark”) reactions  Key reaction catalyzed by RuBisCo  Ribulose bisphosphate carboxylase  Most abundant enzyme! 5C CO 2 6C 3C RuBisCo

Photosynthesis CO 2 light H2OH2O O2O2 H+H+ ATPADPNADPHNADP glucose

Which organelle would not be found in a plant cell? a. Chloroplast b. ER c. Mitochondrion d. Golgi e. Nucleus f. none of the above

light glucose ATP

Respiration & photosynthesis: similarities  Harvest energy in usable forms  Electron transport  Multi-step biochemical pathway  Oxidation-reduction O2O2