Chapter 8: Photosynthesis

ATP: The Energy unit of the Cell ATP (adenosine triphosphate, 三磷酸腺苷） O O O O CH 2 H OH H N HH O N C HC N C C N NH 2 Adenine Ribose Phosphate groups O O O O O O CH

Cell Energy use in Active Transport

Energy is released from ATP ( kJ/mol) –When the 3rd phosphate bond is broken

Trapping Energy from Sunlight The process that uses the sun’s energy to make simple sugars is called photosynthesis Bases of all ecosystems on Earth 6 CO H 2 O + Light energy  C 6 H 12 O O 2

Vein Leaf cross section Mesophyll CO 2 O2O2 Stomata Where Does CO 2 come from? Enters leafs through the stomata Where does H 2 O come from? Absorbed by roots and pulled up to the leaves by cohesion and adhesion (transpiration)

Where does Light Energy come from? Energy from the sun must be absorbed by pigments, light absorbing molecules Inside a chloroplasts are thylakoids and inside their membranes are pigments What wavelength of light do the pigments not absorb? –Green; reason why plants are green

Photosynthesis: 2 Reaction Set 1)Light-dependent reactions  chemical reactions driven by light energy absorbed by pigments 2)Light-independent reactions  chemical reactions that use ATP and NADPH to create sugars out of CO 2

H2OH2O CO 2 Light LIGHT REACTIONS CALVIN CYCLE Chloroplast [CH 2 O] (sugar) NADPH NADP  ADP + P O2O2 ATP

The Light-Dependent reactions Light Reflected Light Chloroplast Absorbed light Granum Transmitted light Pigments- light absorbing molecules Chlorophyll  main light absorbing pigment Light-dependent reactions are broken into two systems: Photosystem II and Photosystem I

Photosystem II Chlorophyll absorbs light energy into electrons Electrons passed through protein carriers (Electron Transport Chain) Energy used to move H + into thylakoid Photosystem II breaks water (photolysis) to get more electrons and H +  produces O 2

Photosystem I Electrons re-energized by chlorophyll in the photosystem Electrons passed to enzyme to change NADP + (nicotinamide adenin dinucleotide phosphate) into NADPH NADPH carries H + and energized electrons to light-independent reactions ATP synthase uses H + ions in thylakoid to make ATP

ATP-Synthase Makes ADP + P i into ATP Powered by Chemiosmosis: –Movement of chemicals across a selectively- permeable membrane –H + concentration gradient was made by photosystem II, now it is used to make ATP through facilitated diffusion 3H + = 1 ATP

The Light-Dependent reactions Photolysis

H2OH2O CO 2 Light LIGHT REACTIONS CALVIN CYCLE Chloroplast [CH 2 O] (sugar) NADPH NADP  ADP + P O2O2 ATP

The Light-Independent reactions

Final Numbers UseProduce Light-Dependent Reactions SunlightNADPH H2OH2OATP NADP+/ADP/PiO2O2 UseProduce Light-Independent Reactions (Calvin Cycle) NADPH RuBP (recycled to keep cycle going) ATPPGAL (Which form sugars) CO 2 NADP+/ADP/Pi

Alternate Pathways: C 4 and CAM Plants in hot/dry areas lose H 2 O quickly if they open their stomata but they need CO 2 2 Pathways to fix this: 1)C 4  allows plant to change O 2 into CO 2 but it costs ATP so it is less energy efficient Corn and sugar cane 2)CAM  Collect CO 2 at night and store it as an acid then use the acid to make CO 2 during the day time Pineapple trees and cactus plants

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Homework Read Ch. 9 and do Ch. 9 vocabulary Ch. 8 Apply Vocabulary and Questions 1-18 on p