Photosynthesis Ch 7

Autotrophs

Chloroplasts Contain chlorophyll – Green Site of photosynthesis Concentrated in leaves

Chloroplast Structure

Overview of Photosynthesis Light Reaction (stage 1) – Thylakoid membranes of granna – Converts light energy to chemical energy – O 2 produced as waste product Calvin Cycle (stage 2) – Stroma – Synthesizes sugar molecules with CO2 & energy produced in light reactions

Fig H2OH2O ADP P LIGHT REACTIONS (in thylakoids) Light Chloroplast NADPH ATP O2O2 CALVIN CYCLE (in stroma) Sugar CO 2  NADP +

Redox (again) Recall – Oxidation- loss of e- – Reduction- addition of e- 6 CO H 2 O C 6 H 12 O O 2 Reduction Oxidation

Light Reactions Wavelength (nm) 10 –5 nm Increasing energy Visible light 650 nm 10 –3 nm 1 nm10 3 nm 10 6 nm 1 m Radio waves Micro- waves Infrared X-rays UV Gamma rays

Light Absorbing Pigments Chlorophyll A Chlorophyll B Carotenoids

Photosystems Reaction center complex e–e– Primary electron acceptor Light-harvesting complexes Photon Transfer of energy Pigment molecules Pair of Chlorophyll a molecules Thylakoid membrane

Chlorophyll is excited Chlorophyll molecule Excited state Ground state Heat Photon (fluorescence) e–e–

Photosystems

Fig. 7-8a Stroma O2O2 H2OH2O 1212 H+H+ NADP + NADPH Photon Photosystem II Electron transport chain Provides energy for synthesis of by chemiosmosis + 2 Primary acceptor 1 Thylakoid mem- brane P Thylakoid space e–e– e–e– 5 Primary acceptor P700 6 Photon Photosystem I ATP H+H+ +

Fig O2O2 H2OH2O 1212 H+H+ NADP + H+H+ NADPH + 2 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+ Photosystem II Photosystem I Electron transport chain ATP synthase Light Stroma (low H + concentration) Chloroplast Thylakoid membrane Thylakoid space (high H + concentration) ADP + PATP

Calvin Cycle CO 2 ATP NADPH Input CALVIN CYCLE G3POutput:

Carbon Fixation - Stomata

NADPH ATP RuBP 3 P G3P P Input: CO 2 1 Rubisco 3 P Step Carbon fixation 3-PGA 6 P C ALVIN CYCLE P Step Reduction 2 2 G3P 5 P P Glucose and other compounds Output: Step Release of one molecule of G3P 1 Step Regeneration of RuBP 4 4 ATP 3 3 ADP NADP + 6 ADP +

Adaptations CO 2 CALVIN CYCLE Bundle- sheath cell 3-C sugar C 4 plant 4-C compound CO 2 CALVIN CYCLE 3-C sugar CAM plant 4-C compound Night Day Mesophyll cell CO 2

Environmental Impacts Atmosphere Sunlight Some heat energy escapes into space Radiant heat trapped by CO 2 and other gases

Photosynthesis and cellular respiration provide energy for life – Photosynthesis uses solar energy to produce glucose and O 2 from CO 2 and H 2 O – Cellular respiration makes ATP and consumes O 2 during the oxidation of glucose to CO 2 and H 2 O CO 2 H2OH2O Glucose O2O2 ATP ECOSYSTEM Sunlight energy Photosynthesis in chloroplasts Cellular respiration in mitochondria (for cellular work) Heat energy   Figure 6.1