BIO 41,Ch7

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  1. Photosynthesis
    Process whereby plants, algae (which are protists), & certain bacteria transform light energy into chem energy, using carbon dioxide & water as starting materials
  2. In addition to CO2, Photosynthesis requires ______, which is absorbed by plant's roots & transported to leaves, where veins carry it to photosynthetic cells
  3. Chem energy produced via photosynthesis is stored in bonds of what?
    Sugar molecules
  4. Photosynthesis takes place w/in organeles called _____ using gases that are exchanged via pores called ______.
    chloroplasts; stomata
  5. Chloroplasts
    • Light-absorbing organelles that are concentrated in interior cells of leaves
    • All green parts of plant/algae contain these & convert sunlight into chem energy in Photosynthesis
    • In most plants, however, the leaves have most chloroplasts & are therefore major locations of photosynthesis (about 500,000 per square millimeter of leaf surface)
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  6. Chlorophyll (Green color on leaves)
    • Selective absorption of other colors while reflecting/transmitting green light
    • Light-absorbing pigment in chloroplasts that plays central role in converting solar energy to chem energy
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  7. Stomata
    • Tiny pores (singular, stoma, meaning "mouth")
    • Carbon dioxide (CO2) enters, & oxygen (O2) exits these
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  8. Chloroplasts have a double-membrane envelope, just like a what?
  9. Membranes w/in chloroplast form framework where many of the reactions of......
    ....photosynthesis occur
  10. Stroma
    • A Thick fluid
    • Chloroplast's inner membrane encloses compartment filled w/ this fluid
  11. Thylakoids
    • Interconnected mambranous sacs suspended in stroma
    • --- Chlorophyll molecules that capture light energy are built into this
  12. Grana
    • Stacks where thylakoids are concentrated
    • (singular, granum)
  13. Structure of Chloroplast
    • Aids its function by providing large surface area for reactions of photosynthesis, w/ its stacks of disks
    • Chemical factories powered by the sun
  14. Chem equation: Relationship between Photosynthesis & Cellular respiration
    • ---Photosynthesis Reactants: CO2, H2O (are also waste products of cellular respiration)
    • ---Photosynthesis produces what Respiration uses: C6H12O6(Glucose) & O2(Oxygen)
    • Photosynthesis takes "exhaust" of cellular respiration & rearranges its atoms to produce food & oxygen
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  15. In Photosynthesis, electrons are boosted _______ & added to CO2 to produce sugar, as a pose to cellular respiration causing their electrons to "fall"

    • -NEXT: Hydrogen moves along w/ electrons, so.....Redox process: Hydrogen transfer from H2O to CO2; this transfer requires chloroplast to split water molecules into hydrogen & oxygen.
    • -THEN: Hydrogen is transfered w/ electrons to CO2 to form sugar
    • -FINALLY: Xxygen escaped thru stomata into atmosphere as O2= Wast Product of Photosynthesis
  16. 2 Stages of Photosynthesis:
    • Calvin CYCLE
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  17. Stage 1 Photosynthesis: LIGHT REACTIONS
    • Chlorophyll in thylakoid membranes absorbs solar energy, then is converted to chem energy ATP & NADPH
    • Water is split providing a source of electrons & giving off O2 gas as by-product
  18. NADPH
    • Electron carrier in Photosynthesis
    • Light drives electrons from chlorophyll to NADP+(oxidized form of carrier), forming NADPH (reduced form of carrier)
    • Provides high-energy electrons for reduction of CO2 to sugar in Calvin cycle
  19. Stage 2 Photosynthesis: Calvin CYCLE
    • Uses products of light reactions to power production of sugar from CO2
    • Enzymes from cycle are dissolved in stroma(thick fluid in chloroplast)
    • Indirectly DEPENDS on Light to produce sugar because it Requires: ATP (Sugar Synthesis Energy) & NADPH (High-Energy Electrons for Reduction of CO2 & Glucose) BOTH produced by LIGHT REACTIONS
  20. Sunlight
    • Type of energy called Radiation, or Electromagnetic Energy
    • Travels thru space as rhythmic waves; Analogous to ripples that are made by pebble dropped into pond
  21. Wavelength
    Distance between crests of 2 adjacent waves
  22. Electromagnetic Spectrum
    • Full range of radiation (From very short wavelengths of gamma rays to very long wavelengths of radio signals)
    • Visible light is small fraction of spectrum (Consists of wavelengths our eyes see as diff colors)

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  23. When sunlight shines on pigmented material, certain wavelengths (colors) of the visible light are...
    • ...absorbed & disappear from light that's reflected by material
    • **Ex: Pair of Blue jeans, Pigments in fabric absorb other colors, leaving only light in blue part of spectrum to be reflected from fabric to our eyes
  24. Theodor Engelmann
    • German biologist OBSERVED that "Certain bacteria living in water tend to cluster in areas w/ higher oxygen concentration" in 1883
    • He knew light passed thru PRISM & separated into diff wavelengths (colors)
  25. What did Theodor Engelmann QUESTION?
    His info to determine which wavelengths of light work best for photosynthesis
  26. Theodor Engelmann's HYPOTHESIS
    Oxygen-seeking bacteria would congragate near regions of algae performing most photosynthesis (Producing most Oxygen)
  27. Theodor Engelmann's EXPERIMENT
    • Laid a string of freshwater algal cells w/in a drop of water on microscope slide.
    • Then added oxygen-sensitive bacteria to drop
    • Next, using prism, created spectrum of light & shined it on slide
    • RESULTS: Most bacteria congregated around algae exposed to red-orange & blue-violet light, w/ very few bacteria moving to green light
  28. Other than Theodor Engelmann's Main EXPERIMENT, what did his other experiments verify?
    That Chloroplasts absorb light mainly in blue-violet & red-orange part of spectrum & those wavelengths of light are ones mainly responsible for Photosynthesis
  29. Chloroplasts contain how many kinds of pigments?
  30. Chloroplast Pigment: Chlorophyll a
    • Absorbs mainly blue-violet & red light
    • Participate directly in light reactions
  31. Chloroplast Pigment: Chlorophyll b
    • Absorbs mainly blue & orange light
    • Doesn't participate directly in light reactions, but it broadens range of light that plant can use by conveying absore energy to chlorophyll a
    • It then puts energy to work in light reactions
  32. Chloroplast Pigment: Carotenoids
    • Family of yellow-orange which absorb mainly blue-green light
    • Some pass energy to chlorophyll a
    • **Protective Function of Other Carotenoids: They absorb & dissipate excessive light energy that would otherwise damage chlorophyll (Similar Carotenoids, which we get from carrots & certain other plants,┬ámay help protect our eyes from bright light)
  33. The falling autumn temp's cause an increase or decrease in levels of chlorophyll?
    • Decrease
    • **This allows color of longer-lasting carotenoids to show thru
  34. Chloroplast pigments are all built into thylakoid membranes, which are organized into light-harvesting complexes called?
  35. Photon
    • Fixed quantity of light energy; Discrete packets of energy
    • --The SHORTER the wavelength of light, GREATER the energy of Photon
    • **Ex: Photon of Violet light packs nearly 2x as much energy as Red light Photon
  36. When a pigment molecule absorbs a photon, one of pigment's electrons gains energy, & electron has become what?
    • "excited"
    • -- The electron has been raised from Ground State to an Excited State, which is HIGHLY UNSTABLE; so an Excited Elec. usually loses its excess energy & FALLS BACK to its Ground State almost Immediately
    • -- Most pigments merely Release HEAT ENERGY as their light-excited electrons FALL BACK (Black Auto Hood gets HOT on Sunny Day)
  37. The fluorescent light emitted by a glow stick is caused by a chemical reaction that excites electrons of a fluorescent dye. So....
    electrons quickly FALL BACK Down to Ground State, releasing energy in form of fluorescent light
  38. Photosystem
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    • Light-gathering antenna that focuses light energy onto a reaction center
    • Has cluster of a few hundred pigment molecules, including chlorophylls a & b & some carotenoids == This cluster of pigment molecules functions as Light-gathering antennaImage Upload 8
  39. Photosystem: Reaction Center & Primary Electron Acceptor
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    When photon strikes 1 of the pigment molecules, energy jumps from molecule to molecule until it arrives at REACTION CENTER: Consists of a chlorophyll a molecule that sits next to another molecule called PRIMARY ELECTRON ACCEPTOR: Traps light-excited electron from chlorophyll a in reaction center.
  40. How Light Reactions Generate ATP & NADPH
    • 1.) Photons excite electrons in chlorophyll of water-splitting Photosystem, THEN Photons are trapped by PRIMARY ELECTRON ACCEPTOR. Water-splitting Photosystem replaces its light-excited electrons by extracting electrons from water, which RELEASES O2 during Photosynthesis
    • 2.) Energized electrons from water-splitting Photosystem pass down an ETC to NADPH-producing Photosystem, Chloroplast uses energy released by electron "fall" to make ATP
    • 3.) NADPH-producing Photosystem transfers its light-excited electrons to NADP+, reducing it to NADPH
    • ***2 Types of PHOTOSYSTEMS cooperate in Light Reactions
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  41. C4 Plants
    • --They incorporate carbon from CO2 into 4-Carbon compound before proceeding to Calvin cycle
    • When it's hot/dry weather, it keeps its Stomata mostly closed, conserving water
    • BUT has enzyme that continues to incorporate carbon even when leaf's CO2 concentration is low (donates CO2 to Calvin cycle to nearby cell)
    • **Ex: sugarcane, corn
  42. CAM plants
    • CO2 is incorporated into 4-Carbon compound that banks it at Night & releases to Calvin cycle in Same Cell during day, Keeps Photosynthesis Going when Stomata's closed during daytime
    • Adapted to VERY DRY weather
    • Conserves water by opening stomata & admitting CO2 ONLY at night
    • **Ex: Pineapples, cacti, succulent (water-retaining) plants ALOE & JADE
  43. C3 Plants
    • The first organic compound produced in Calvin Cycle is 3-Carbon molecule
    • Widely distributed
    • Farmers face issue of growing it cause plants close their stomata on hot, dry days, REDUCING water loss but also prevents CO2 from entering leaves; Sugar Production CEASES
    • **Ex(Common Crops): Soybeans, Oats, Wheat, Rice
  44. Location of Light Reactions in Thylakoid Membrane
    • 2 Photosystems & ETC that connects them transfer electrons from H2O-->NADP+, reducing it to NADPH
    • NOTE: Mechanism of ATP Production during light reacitons VERY SIMILAR to Mechanism in Cell Respir.
    • In both cases, An ETC pumps Hydrogen Ions (H+) across a membrane-----Inner Mitochondrial Membrane in the case of Respiration & Thylakoid membrane in Photosynthesis
    • ALSO, ATP synthases use energy stored by H+ gradient to make ATP
    • MAIN DIFFERENCE: Food provides high-energy electrons in Cell Respir, whereas light-excited electrons flow down Transport Chain during Photosynthesis
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  45. Hard-hat Analogy for Light Reacitons
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    • Light Reactions absorb Solar Energy == Chem energy of ATP & NADPH
  46. Calvin Cycle: Makin Sugar from Carbon Dioxide
    • Functions like Sugar Factory w/in Stroma of Chloroplast
    • INPUTS: CO2 (Using its C) from air, as well as ATP (Using it Energy) & NADPH (Using its High-Energy Electrons)
    • Cycle constructs energy-rich sugar molecule====>Output
    • OUTPUT: *G3P (Glyceraldehyde 3-Phosphate)
    • Plant cell uses G3P as Raw material to make Glucose & other organic compounds (Cellulose, Starch) that it needs
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Card Set:
BIO 41,Ch7
2013-04-26 23:37:11
Photosynthesis Chapter Bio

Photoynthesis: Using Light to Make Food
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