How Cells Acquire Energy

1. Carbon and Energy Sources How Cells Acquire Energy • ____________- • Carbon source is _______________ • Energy source is ___________ • _______________ • Get carbon and energy by eating __________ or _______________ Plants, some bacteria, many protistans Chapter 6

2. T.E. Englemann’s Experiment Background • Certain bacterial cells will move toward places where oxygen concentration is high • Photosynthesisproduces oxygen Hypothesis • Movement of bacteria can be used to determine optimal light wavelengths for photosynthesis Method • Algal strand placed on microscope slide and illuminated by light of varying wavelengths • Oxygen-requiringbacteria placed on same slide

3. Results • Bacteria congregated where red and violet wavelengths illuminated alga Conclusion Bacteria moved to most effective light for photosynthesis

4. ______________ Energy-storing pathway Releases _______ Requires ______ ________ _______________ Energy-releasing pathway Requires _______ Releases carbon dioxide Linked Processes LIGHT ENERGY ___ + _____+ _____ ____ + _____ oxygen glucose water carbon dioxide water

5. Visible Light • Wavelengths humans perceive as different ______ • Violet (___ nm) to red (____ nm) • Longer wavelengths, lower energy shortest longest Of the energy that reaches Earth’s surface, about ___ is intercepted by photoautotrophs

6. Photons • Packets of ______ energy • Photons with most energy travel as ________ wavelength (blue-green light) Pigments • Light-absorbing ________ • Absorb some wavelengths and ________ others • Color you see are the wavelengths ___ absorbed chlorophyll a chlorophyll b Wavelength (nanometers)

7. Plants contain 4 main pigments • _______________-reflect green- most common • ___________- reflect red/yellow • Includes xanthophiles and carotenes • ______________- give flowers their colors • __________- in red algae

8. In bacteria- pigments are in ____________ 2 Photosystems and Electron Transporters • In plants- pigments are in _________ _____________ of chloroplasts water-splitting complex thylakoid compartment H2O 2H + 1/2O2 P680 P700 acceptor acceptor PHOTOSYSTEM II pool of electron transporters stroma PHOTOSYSTEM I

9. Two _______ of Photosynthesis sunlight water uptake carbon dioxide uptake ATP ADP + Pi 1. ________ ________- _________ 2. _______ ______- _______ NADPH NADP+ glucose P • Pigments absorb ____ energy • _____split • ___ and _____ formed • _______ released • CO2 converted to _____ • Can proceed in the _____ • ___________ cycle oxygen release new water

10. 1. LIGHT DEPENDENT-REACTIONS ….but all energy is funneled into ______ _______ Many _______ capture energy… reaction center (a specialized chlorophyll a molecule) Then an electron is sent to the ________

11. 1. LIGHT DEPENDENT-REACTIONS In ET system, ATP is produced ATP

12. In ET system: • two photosystems: ______ and ______ 1. LIGHT DEPENDENT-REACTIONS H2O photolysis e– e– ATP SYNTHASE NADPH NADP+ ATP ADP + Pi PHOTOSYSTEM II PHOTOSYSTEM I • End result- • _______regenerated • ____ is concentrated inside • _____ made when H+ is moved across membrane

13. CO2 _________ ATP ______ NADPH ________ 6 CO2 (from the air) Calvin- Benson Cycle CARBON FIXATION 6 6 RuBP unstable intermediate 12 PGA 6 ADP 12 ATP 6 ATP 12 NADPH 4 Pi 12 ADP 12 Pi 12NADP+ P-glucose 10 PGAL 12 PGAL 2 PGAL Pi _______ _______ P glucose

14. Alternative mechanisms of carbon fixation have evolved in hot, arid climates • The _______ are not only the major route for gas exchange (CO2 in and O2 out), but also for the evaporative loss of _______. • On hot, dry days plants close the stomata to conserve water, but this causes problems for photosynthesis. Solution # 1 C3 plants- • ____________- fix ___ (Not CO2) • But photorespiration can drain away as much as _____ of the carbon fixed by the Calvin cycle

15. Solution # 2 Solution # 3 __________ ___________ e.g. pineapple e.g. sugarcane Fix CO2 as other ____________, then use as needed Fix CO2 as other molecules at _____, then use during ____

16. Summary of Photosynthesis light LIGHT-DEPENDENT REACTIONS 6O2 12H2O ATP NADP+ NADPH ADP + Pi PGA CALVIN-BENSON CYCLE PGAL 6CO2 RuBP P C6H12O6 (phosphorylated glucose) end product (e.g. sucrose, starch, cellulose)