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  • 1. Photosynthesis and Cellular Respiration
  • 2. Energy In Living Systems Section 9-1
  • 3. Energy in Living Things
    • Living things must maintain homeostasis, therefore require a constant energy input
    • Energy stored in chemical bonds of carbohydrates and other molecules
  • 4. Autotrophs vs. Heterotrophs
    • Organisms that manufacture their own food are autotrophs . Others are heterotrophs .
    • All life depends on autotrophs.
  • 5. The Carbon Cycle
    • Carbon atoms used by organisms to CREATE organic compounds, which are then broken down for energy.
    • Examples: carbohydrates used for energy, coal burned in power plants, forest fires
  • 6.  
  • 7. Photosynthesis
    • Photosynthesis is the process by which light energy is converted to chemical energy through a series of reactions called a “biochemical pathway”
    • Biochemical Pathway – sequence in which the product of one step is used in the next
  • 8. Overview of Photosynthesis
    • Light energy, Carbon dioxide, and Water are used.
    • Glucose (carbohydrate) and oxygen gas are produced.
  • 9. Respiration
    • Respiration is the process in which organisms USE energy.
    • Products of photosynthesis are used in respiration.
  • 10. Photosynthesis Respiration Light Energy organic compounds and oxygen carbon dioxide and water AUTOTROPHS HETEROTROPHS AND AUTOTROPHS
  • 11. Transferring Energy
    • When food is broken down, cells use energy to make ATP
    • ATP: adenosine triphosphate, main energy source for cellular processes
      • “ energy currency”
  • 12. Adenosine Triphosphate
  • 13. ATP Sythase
    • ADP (adenosine diphosphate) is low energy form
    • ADP + Phosphate  ATP
    • Catalyzed by enzyme ATP Synthase
  • 14. Photosynthesis Section 9-2
  • 15. 1: Light Absorbed
    • Initial reactions = LIGHT REACTIONS
    • Light absorbed by chloroplasts . (Plant cells may have 50 or more chloroplasts.)
    • Important structures within chloroplasts include flattened sacs called thylakoids
  • 16. Chlorophyll
    • Within the membrane around the thylakoids, chlorophyll absorbs certain types of light.
    • When plants lose their green chlorophyll in autumn, other pigments show.
  • 17. REMINDER!
    • Electrons are a tiny, energetic part of an atom.
  • 18. 2: Electrons Excited
    • Chlorophyll molecules are grouped into structures called photosystems (“reaction centers”)
    • Light absorbed excites electrons in photosystem II.
  • 19. 3: Electron Transport
    • Electrons passed down electron transport chains.
  • 20. 4: Replacing Electrons
    • Water molecules are broken down in photosystem
    • 2H 2 O  4H + + 4e - + O 2
    • Oxygen released to air.
    • Electrons replace those used in light reactions
    • Some energy used to pump additional H + into thylakoid
  • 21. 5: Making ATP
    • Proton concentration in thylakoid HIGH
    • Diffusion of protons outward powers ATP synthase protein
  • 22. 6: Making NADPH
    • Second electron transport chain (beginning with photosystem I)
    • High energy, like ATP
  • 23. We’re Halfway Done…
    • After doing through the LIGHT REACTIONS, chloroplasts are filled with tons of ATP and NADPH, which store lots of energy. However, these can only be used within a cell.
    • So far:
    • IN: H 2 O and light
    • OUT: ATP, NADPH, and O 2
  • 24. Photosynthesis
    • First set of reactions = light reactions = electron transport
    • Second set of reactions = dark reactions = Calvin Cycle
  • 25. The Calvin Cycle
    • a.k.a. the “dark reactions”
    • Accomplishes “carbon fixation” taking carbon from inorganic molecules and putting it into organic molecules (CO 2  sugars)
  • 26. Calvin Cycle Overview
    • Carbon dioxide (CO 2 ) diffuses into the area around the thylakoids (called the stroma ).
    • Plant cells use ATP and NADPH to convert CO 2 into carbohydrates.
  • 27. Steps of Calvin Cycle
    • CO 2 added to five-carbon compound (x3)
    • Six-carbon sugars split in half, and phosphates from NADPH and ATP are added
  • 28. Steps of Calvin Cycle
    • One three-carbon sugar used to make an organic molecule
    • Remaining three-carbon sugars are recycled and rearranged (using energy from ATP) to begin the cycle again
  • 29.  
  • 30.  
  • 31. Rates of Photosynthesis
  • 32. What things might affect how much energy plants make?
  • 33. Rate of Photosynthesis
    • Higher light intensity makes more electrons excited (electron transport chain)
    • More intense light means a higher rate of photosynthesis
  • 34. Rate of Photosynthesis
    • Increased levels of carbon dioxide in the atmosphere increases the rate of photosynthesis
  • 35. Rate of Photosynthesis
    • Moderately high temperatures accelerate chemicals involved
    • Extremely high temperatures make these molecules unstable and ineffective
    • This results in a “peak” temperature
  • 36.
    • A famous scientist once said that wherever in the universe life exists, some of those life forms must be colored. Why would the scientist make such a statement?
    • All of the major components of the light reactions, including the pigment molecules clustered in photosystems I and II, are located in the thylakoid membrane. What is the advantage of having these components confined to the same membrane rather than dissolved in the stroma or cytoplasm?
    • What time of year do you think green plants (especially trees) need the most energy? Discuss the light intensity and normal temperatures at that time. Do they favor high levels of photosynthesis? Why or why not?