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How Cells Acquire Energy

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Presentation on theme: "How Cells Acquire Energy"— Presentation transcript:

1 How Cells Acquire Energy
Chapter 6

2 (see next slide) leaf’s upper surface photosynthetic cells
two outer layers of membrane inner membrane system (thylakoids, all interconnecting bychannels) (see next slide) Fig. 6.3a, p. 94 stroma

3 Organelles of photosynthesis
Chloroplasts Organelles of photosynthesis

4 Photosynthesis Equation
LIGHT ENERGY 12H2O + 6CO2 6O2 + C2H12O6 + 6H2O water carbon dioxide oxygen glucose water

5 Two Stages of Photosynthesis
sunlight water uptake carbon dioxide uptake ATP LIGHT DEPENDENT-REACTIONS ADP + Pi LIGHT INDEPENDENT-REACTIONS NADPH NADP+ P glucose oxygen release new water

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

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

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

9 Pigment Structure 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

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 complex thylakoid compartment H2O 2H + 1/2O2 P680 P700 acceptor acceptor PHOTOSYSTEM II pool of electron transporters stroma PHOTOSYSTEM I

13 Light-Dependent Reactions
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

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 e– e– ATP e– e– electron acceptor
electron transport system e– ATP e– e–

16 Machinery of Noncyclic Electron Flow

17 Potential to transfer energy (voids)
Energy Changes second transport system e– NADPH first e– transport system e– Potential to transfer energy (voids) e– (PHOTOSYSTEM I) (PHOTOSYSTEM II) H2O 1/2 O2 + 2H+

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

19 unstable intermediate
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+ 10 PGAL 12 PGAL 2 PGAL Pi P glucose

20 animation

21 Summary of Photosynthesis
LIGHT-DEPENDENT REACTIONS light 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)

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