PHOTOSYNTHESIS

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PHOTOSYNTHESIS
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I. Autotrophs and Heterotrophs

• A. Energy for living things comes from the SUN
• B. Plants and other organisms use light energy
  from the sun to produce food
• C. Autotrophs- make their own food
• Ex plants

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• Heterotrophs- cannot use sun energy to make
  their
• food and obtain it from the foods they
  consume
• Ex leopards, mushrooms

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Chemical Energy and ATP

• To live, organisms must release energy in sugars
  and other compounds
• Energy- light, heat
• Energy can be stored in compounds
• Exothermic reaction

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• B. ATP
• adenosine triphosphate
• chemical compound used to store energy

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Releasing energy from ATP

• Stored energy is released from ATP when ATP is
  broken down into ADP Phosphate
• Add/subtract Phosphate and you can store/release
  ENERGY!

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Using Biochemical energy

• The characteristics of ATP that make it a useful
  to all types of cells as their basic energy
  source.
• When is ATP used?
• Active transport
• Powers movement inside cell microtubules use
  energy

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• Sooo energy is either MADE through
  photosynthesis or consumed
• Energy is USED in process called cellular
  respiration

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Light Pigments

• In addition to water CO2, photosynthesis
  requires LIGHT and CHLOROPHYLL, a molecule in
  chloroplasts
• Sunlight is white but contains mixtures of
  visible wavelengths
• Plants gather suns energy using light-absorbing
  molecules called PIGMENTS

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Leaves absorb blue-violet red-orange light
very well - Green light is reflected- why
plants look green!
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Chlorophyll a Absorbs all colors of light except green Plays major role in light reactions of photosynthesis
Chlorophyll b Appears yellow-green Absorbs additional light
Xanthophyll In carotenoid family Yellow Fat soluble
Carotene Accessory pigments Red orange pigments
Major Pigments- use light energy directly Accessory Pigments- pass absorbed light energy to chlorophyll
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LOCATION OF PHOTOSYNTHESIS
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Role of Pigments

• When chlorophyll absorbs light, much of the
  energy is transferred to raising the energy level
  of ELECTRONS in the CHLOROPLASTS
• These electrons power photosynthesis

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EQUATION
Inputs Light, carbon dioxide, water Outputs
sugar and oxygen
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CHLOROPLAST STRUCTURE

• Chloroplast has double membrane
• Thylakoids sac-like photosynthetic
• membranes
• Arranged in stacks called GRANA
• Have clusters of chlorophyll and other pigments
• Stroma Fluid area surrounding
• thylakoids

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• Light-Dependent
• takes place in
• thylakoids
• Calvin Cycle
• takes place in
• stroma

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Light Reaction

• Chlorophyll molecules in thylakoid capture light
  energy
• This energy releases electrons from H2O
• H2O then splits into O2 and H
• Oxygen is a "waste product" escapes to the
  atmosphere

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So what happens to the electrons and hydrogen
ions?

• Chloroplasts use them to make an energy-rich
  molecule called NADPH and ATP
• The overall result of the light reaction?
• Light Oxygen NADPH ATP

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• ATP and NADP are recycled back into the system
• Light reaction is charging up the battery
  needed to synthesize sugars in Calvin Cycle

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Calvin Cycle

• Does NOT use light at all
• Process to store energy that was made in light
  cycle in the form of sugar

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The Calvin Cycle

1. The enzymes for the Calvin cycle are located
   outside the thylakoids dissolved in the STROMA.
2. Uses CO2 and energy powered by ATP and NADPH to
   produce sugar
3. NAPDH and ATP are recycled back to the Light
   Cycle for recharging

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Reactants
Products
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Two Processes
Calvin Cycle
Light Reaction
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Factors Affecting Photosynthesis

• Shortage of raw materials
• Temperature
• Light intensity