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

T.E. Englemann’s Experiment Background Certain bacterial cells will move toward places where oxygen concentration is high Photosynthesis produces 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-requiring bacteria placed on same slide

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

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

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

Wavelength (nanometers) 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)

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

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

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

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 ________

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

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

unstable intermediate Calvin- Benson Cycle 6 CO2 (from the air) CARBON FIXATION 6 6 RuBP unstable intermediate CO2 _________ ATP ______ NADPH ________ 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

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

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

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