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How Cells Acquire Energy Chapter 6. Fig. 6.3a, p. 94 leafs upper surfacephotosynthetic cells two outer layers of membrane inner membrane system (thylakoids,

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Presentation on theme: "How Cells Acquire Energy Chapter 6. Fig. 6.3a, p. 94 leafs upper surfacephotosynthetic cells two outer layers of membrane inner membrane system (thylakoids,"— Presentation transcript:

1 How Cells Acquire Energy Chapter 6

2 Fig. 6.3a, p. 94 leafs upper surfacephotosynthetic cells two outer layers of membrane inner membrane system (thylakoids, all interconnecting bychannels) stroma (see next slide)

3 Organelles of photosynthesis Chloroplasts

4 Photosynthesis Equation 12H 2 O + 6CO 2 6O 2 + C 2 H 12 O 6 + 6H 2 O watercarbon dioxide oxygenglucose water LIGHT ENERGY

5 Two Stages of Photosynthesis sunlightwater uptakecarbon dioxide uptake ATP ADP + P i NADPH NADP + glucose P oxygen release LIGHT INDEPENDENT- REACTIONS LIGHT DEPENDENT- REACTIONS new water

6 Electromagnetic Spectrum Shortest Gamma rays wavelength X-rays UV radiation Visible light Infrared radiation Microwaves LongestRadio waves wavelength

7 Visible Light Wavelengths humans perceive as different colors Violet (380 nm) to red (750 nm) Longer wavelengths, lower energy

8 Pigments Light-absorbing molecules Absorb some wavelengths and transmit others Color you see are the wavelengths NOT absorbed Wavelength (nanometers) chlorophyll b chlorophyll a

9 Light-catching part of molecule often has alternating single and double bonds These bonds contain electrons that are capable of being moved to higher energy levels by absorbing light Pigment Structure

10 Excitation of Electrons Excitation occurs only when the quantity of energy in an incoming photon matches the amount of energy necessary to boost the electrons of that specific pigment Amount of energy needed varies among pigment molecules

11 Pigments in Photosynthesis Bacteria –Pigments in plasma membranes Plants –Pigments embedded in thylakoid membrane system –Pigments and proteins organized into photosystems –Photosystems located next to electron transport systems

12 Photosystems and Electron Transporters water-splitting complexthylakoid compartment H2OH2O2H + 1/2O 2 P680 acceptor P700 acceptor pool of electron transporters stromaPHOTOSYSTEM II PHOTOSYSTEM I

13 Pigments absorb light energy, give up e - which enter electron transport systems Water molecules are split, ATP and NADH are formed, and oxygen is released Pigments that gave up electrons get replacements from splitting water Light-Dependent Reactions

14 Electron Transport System Adjacent to photosystem Acceptor molecule donates electrons from reaction center As electrons flow through system, energy they release is used to produce ATP and, in some cases, NADPH

15 Cyclic Electron Flow electron acceptor electron transport system e–e– e–e– e–e– e–e– ATP

16 Machinery of Noncyclic Electron Flow photolysis H2OH2O NADP + NADPH e–e– ATP ATP SYNTHASE PHOTOSYSTEM IPHOTOSYSTEM II ADP + P i e–e–

17 Energy Changes Potential to transfer energy (voids) H2OH2O 1/2 O 2 + 2H + (PHOTOSYSTEM II) (PHOTOSYSTEM I) e–e– e–e– e–e– e–e– second transport system NADPH first transport system

18 Synthesis part of photosynthesis Can proceed in the dark Take place in the stroma Calvin-Benson cycle Light-Independent Reactions

19 Calvin- Benson Cycle CARBON FIXATION 6CO 2 (from the air) 66 RuBP PGA unstable intermediate 6 ADP 6 12 ATP NADPH PGAL glucose P PGAL 2 PiPi 12 ADP 12 P i 12NADP P i PGAL

20 animation

21 Summary of Photosynthesis light 6O 2 12H 2 O CALVIN- BENSON CYCLE C 6 H 12 O 6 (phosphorylated glucose) NADPHNADP + ATP ADP + P i PGA PGAL RuBP P 6CO 2 end product (e.g. sucrose, starch, cellulose) LIGHT-DEPENDENT REACTIONS


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